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| Intellectual disability - microarray and sequencing v5.502 | CLEC16A |
Sarah Leigh edited their review of gene: CLEC16A: Added comment: Heterozygous CLEC16A variants have been identified as a genetic risk factor for several autoimmune disorders and for Parkinson disease (PMID: 37175930). PMID: 36538041 reports the neurological effect of homozygous terminating CLEC16A variants in two families. In family 1, the first child died at 5 months, he had progressive microcephaly, failure to thrive and cranial CT showed brain atrophy, dilatation of both central and peripheral liquor spaces, hypoplasia of the corpus callosum (no genetic testing was done), the third pregnancy was terminated (17 weeks of gestation) after prenatal ultrasound showed ventriculomegaly, agenesis of corpus callosum (no genetic testing was done), the fourth pregnancy was also terminated (22 weeks of gestation) as the prenatal ultrasound showed agenesis of corpus callosum. This fetus was homozygous for NM_001243403.1(CLEC16A):c.2062 + 5G > A, RT-PRC showed that this variant resulted in the deletion of exon 19 and a frame shift. Both parents and an unaffected sibling were heterozygous for this variant. In family 2, a single affected child was homozygous for NM_001243403.1(CLEC16A):c.-4_12del, p.Met1fs*. This child had progressive microcephaly, failure to thrive, severe global developmental delay, global brain atrophy and died at 6 years. There is no genetic data from the parents or unaffected siblings in Family 2. PMID: 37175930, also presents zebrafish experiments, where mutagenesis of clec16a by CRISPR–Cas9 resulted in accumulated acidic/phagolysosome compartments, in neurons and microglia, and dysregulated mitophagy. This was rescued by wild type CLEC16A, but not by the C-terminal truncated variant. The authors conclude that dysregulation of CLEC16A-mediated endosomal sorting is associated with neurodegeneration.; Changed rating: GREEN; Changed publications to: 36538041; Changed mode of inheritance: BIALLELIC, autosomal or pseudoautosomal |
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| Intellectual disability - microarray and sequencing v5.495 | SNF8 |
Achchuthan Shanmugasundram changed review comment from: PMID:38423010 reported nine individuals from six families presenting with a spectrum of neurodevelopmental/ neurodegenerative features caused by biallelic variants in SNF8. The phenotypic spectrum included four individuals with severe developmental and epileptic encephalopathy with leukoencephalopathy and early death in three of those cases. Two individuals died too young to develop epilepsy. A second cohort shows a milder phenotype with intellectual disability, childhood-onset optic atrophy, or ataxia. All mildly affected individuals shared the same hypomorphic variant, c.304G>A (p.Val102Ile) as compound heterozygous. Functional studies using fibroblasts derived from patients and zebrafish model showed loss of function as the disease mechanism. Sources: Literature; to: PMID:38423010 reported nine individuals from six families presenting with a spectrum of neurodevelopmental/ neurodegenerative features caused by biallelic variants in SNF8. The phenotypic spectrum included four individuals with severe developmental and epileptic encephalopathy with leukoencephalopathy and early death in three of those cases. Two individuals died too young to develop epilepsy. A second cohort shows a milder phenotype with intellectual disability, childhood-onset optic atrophy, or ataxia. All mildly affected individuals shared the same hypomorphic variant, c.304G>A (p.Val102Ile) as compound heterozygous. Functional studies using fibroblasts derived from patients and zebrafish model showed loss of function as the disease mechanism. This gene has not yet been associated with any phenotypes either in OMIM or in Gene2Phenotype. Sources: Literature |
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| Intellectual disability - microarray and sequencing v5.495 | SNF8 |
Achchuthan Shanmugasundram gene: SNF8 was added gene: SNF8 was added to Intellectual disability - microarray and sequencing. Sources: Literature Mode of inheritance for gene: SNF8 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: SNF8 were set to 38423010 Phenotypes for gene: SNF8 were set to neurodevelopmental disorder, MONDO:0700092; intellectual disability, MONDO:0001071 Review for gene: SNF8 was set to GREEN Added comment: PMID:38423010 reported nine individuals from six families presenting with a spectrum of neurodevelopmental/ neurodegenerative features caused by biallelic variants in SNF8. The phenotypic spectrum included four individuals with severe developmental and epileptic encephalopathy with leukoencephalopathy and early death in three of those cases. Two individuals died too young to develop epilepsy. A second cohort shows a milder phenotype with intellectual disability, childhood-onset optic atrophy, or ataxia. All mildly affected individuals shared the same hypomorphic variant, c.304G>A (p.Val102Ile) as compound heterozygous. Functional studies using fibroblasts derived from patients and zebrafish model showed loss of function as the disease mechanism. Sources: Literature |
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| Intellectual disability - microarray and sequencing v5.446 | ABCC9 | Sarah Leigh Phenotypes for gene: ABCC9 were changed from Cardiomyopathy, dilated, 10, 608569; Atrial fibrillation, familial, 12, 614050; Hypertrichotic osteochondrodysplasia, 239850; CANTU SYNDROME HYPERTRICHOTIC OSTEOCHONDRODYSPLASIA to Intellectual disability and myopathy syndrome, OMIM:619719; intellectual disability and myopathy syndrome, MONDO:0859224 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v5.429 | RARS | Arina Puzriakova Phenotypes for gene: RARS were changed from Cerebral hypomyelination; Global developmental delay; Intellectual disability; Seizures; Cerebral atrophy; Nystagmus; Ataxia; Feeding difficulties to Leukodystrophy, hypomyelinating, 9, OMIM:616140 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v5.345 | KMT2B | Arina Puzriakova Added comment: Comment on list classification: There is sufficient evidence to promote this gene to Green at the next GMS panel update. Inclusion on this panel would also ensure this gene is included on the Paediatric disorders super panel which is appropriate for the phenotype. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v5.337 | CLEC16A |
Dmitrijs Rots gene: CLEC16A was added gene: CLEC16A was added to Intellectual disability - microarray and sequencing. Sources: Literature Mode of inheritance for gene: CLEC16A was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: CLEC16A were set to PMID: 36538041 Phenotypes for gene: CLEC16A were set to severe neurodevelopmental disorder including microcephaly, brain atrophy, corpus callosum dysgenesis, and growth retardation Penetrance for gene: CLEC16A were set to Complete Review for gene: CLEC16A was set to GREEN Added comment: Two independent cases reported PMID: 36538041with biallelic variants and functional evidence. Sufficient for the green rating. Sources: Literature |
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| Intellectual disability - microarray and sequencing v5.291 | DDX23 | Arina Puzriakova Phenotypes for gene: DDX23 were changed from Neurodevelopmental disorder with microcephaly, cerebral atrophy, and visual impairment, OMIM:620066 to Global developmental delay with speech and behavioral abnormalities, MONDO:0030995 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v5.290 | DOHH | Arina Puzriakova Phenotypes for gene: DOHH were changed from DOHH associated neurodevelopmental disorder to Neurodevelopmental disorder with microcephaly, cerebral atrophy, and visual impairment, OMIM:620066 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v5.289 | DDX23 | Arina Puzriakova Phenotypes for gene: DDX23 were changed from Global developmental delay with speech and behavioral abnormalities, MONDO:0030995 to Neurodevelopmental disorder with microcephaly, cerebral atrophy, and visual impairment, OMIM:620066 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v5.271 | ESAM |
Julia Baptista gene: ESAM was added gene: ESAM was added to Intellectual disability - microarray and sequencing. Sources: Literature,Expert Review Mode of inheritance for gene: ESAM was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: ESAM were set to PMID: 36996813 Phenotypes for gene: ESAM were set to severe ID; seizures, spasticity Review for gene: ESAM was set to GREEN Added comment: Lecca et al 2023 reported thirteen patients from eight unrelated families with biallelic loss of function variants (nonsense, frameshift, canonical splice site, all predicted to result in a transcript targeted for nonsense-mediated decay). Protein staining assays in one of the brain fetal samples confirmed loss the loss of protein. The phenotype reported in this cohort is of a severe neurodevelopmental disorder with brain anomalies (calcifications, hydrocephalus, enlarged ventricles, cerebral atrophy, etc), and dysmorphic features. Sources: Literature, Expert Review |
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| Intellectual disability - microarray and sequencing v5.247 | MKL2 | Achchuthan Shanmugasundram commented on gene: MKL2: PMID:37013900 - Two unrelated paediatric cases with de novo variants in MKL2 gene (p.Arg103Gly & p.Ala91Pro) were reported with mild dysmorphic features, severe intellectual disability, global developmental delays, speech apraxia, and impulse control issues. Functional studies in a Drosophila model suggest a gain of function disease mechanism. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v5.224 | AGTPBP1 |
Achchuthan Shanmugasundram gene: AGTPBP1 was added gene: AGTPBP1 was added to Intellectual disability - microarray and sequencing. Sources: Literature Mode of inheritance for gene: AGTPBP1 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: AGTPBP1 were set to 30420557 Phenotypes for gene: AGTPBP1 were set to Neurodegeneration, childhood-onset, with cerebellar atrophy, OMIM:618276 Review for gene: AGTPBP1 was set to GREEN Added comment: PMID:30420557 reported the identification of either homozygous or compound heterozygous variants in AGTPBP1 gene in 13 individuals from 10 unrelated families with infantile‐onset neurodegeneration. Impaired intellectual development was severe, and several patients were unable to speak or have eye contact. This gene has been associated with relevant phenotypes in both OMIM (MIM #618276) and Gene2Phenotype (on DD panel with 'definitive' rating). Sources: Literature |
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| Intellectual disability - microarray and sequencing v5.198 | FOXR1 | Achchuthan Shanmugasundram Phenotypes for gene: FOXR1 were changed from Global developmental delay, HP:0001263; microcephaly, MONDO:0001149; Brain atrophy, HP:0012444 to Global developmental delay, HP:0001263; microcephaly, MONDO:0001149; Brain atrophy, HP:0012444 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v5.198 | FOXR1 | Achchuthan Shanmugasundram Phenotypes for gene: FOXR1 were changed from Global developmental delay, HP:0001263; microcephaly, MONDO:0001149; Brain atrophy, HP:0012444 to Global developmental delay, HP:0001263; microcephaly, MONDO:0001149; Brain atrophy, HP:0012444 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v5.198 | FOXR1 | Achchuthan Shanmugasundram Phenotypes for gene: FOXR1 were changed from Global developmental delay, HP:0001263; microcephaly, MONDO:0001149; Brain atrophy, HP:0012444 to Global developmental delay, HP:0001263; microcephaly, MONDO:0001149; Brain atrophy, HP:0012444 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v5.198 | FOXR1 | Achchuthan Shanmugasundram Phenotypes for gene: FOXR1 were changed from Global developmental delay, HP:0001263; microcephaly, MONDO:0001149; Brain atrophy, HP:0012444 to Global developmental delay, HP:0001263; microcephaly, MONDO:0001149; Brain atrophy, HP:0012444 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v5.197 | FOXR1 | Achchuthan Shanmugasundram Phenotypes for gene: FOXR1 were changed from Global developmental delay, HP:0001263; microcephaly, MONDO:0001149; Brain atrophy, HP:0012444 to Global developmental delay, HP:0001263; microcephaly, MONDO:0001149; Brain atrophy, HP:0012444 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v5.197 | FOXR1 | Achchuthan Shanmugasundram Phenotypes for gene: FOXR1 were changed from Postnatal microcephaly, progressive brain atrophy and global developmental delay to Global developmental delay, HP:0001263; microcephaly, MONDO:0001149; Brain atrophy, HP:0012444 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v5.196 | FOXR1 | Achchuthan Shanmugasundram edited their review of gene: FOXR1: Changed phenotypes to: Global developmental delay, HP:0001263, microcephaly, MONDO:0001149, Brain atrophy, HP:0012444 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v5.187 | TSPOAP1 |
Sarah Leigh gene: TSPOAP1 was added gene: TSPOAP1 was added to Intellectual disability - microarray and sequencing. Sources: Literature,Expert Review Amber Mode of inheritance for gene: TSPOAP1 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: TSPOAP1 were set to 33539324 Phenotypes for gene: TSPOAP1 were set to Dystonia, intellectual disability and cerebellar atrophy |
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| Intellectual disability - microarray and sequencing v5.166 | CLDN5 |
Achchuthan Shanmugasundram changed review comment from: PMID: 36477332 identified de novo heterozygous missense variants in CLDN5 in fifteen unrelated patients who presented with a shared constellation of features including developmental delay, seizures (primarily infantile onset focal epilepsy), microcephaly and a recognizable pattern of pontine atrophy and brain calcifications. Sources: Literature; to: PMID:36477332 reported the identification of de novo heterozygous missense variants in CLDN5 in 15 unrelated patients who presented with a number of clinical features including developmental delay including intellectual disability, seizures (primarily infantile onset focal epilepsy), microcephaly and a recognisable pattern of pontine atrophy and brain calcifications. All seven living patients over four years of age were reported to have intellectual disability. In addition, functional studies from zebrafish model also provided parallel evidence that CLDN5 variants cause a neurodevelopmental disorder involving disruption of the blood brain barrier and impaired neuronal function. This gene has been associated with relevant phenotypes in Gene2Phenotype (CLDN5-related neurodevelopmental disorder with 'limited' rating in the DD panel), but not in OMIM. Sources: Literature |
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| Intellectual disability - microarray and sequencing v5.166 | CLDN5 |
Achchuthan Shanmugasundram gene: CLDN5 was added gene: CLDN5 was added to Intellectual disability - microarray and sequencing. Sources: Literature Mode of inheritance for gene: CLDN5 was set to MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted Publications for gene: CLDN5 were set to 36477332 Phenotypes for gene: CLDN5 were set to epilepsy, MONDO:0005027 Review for gene: CLDN5 was set to GREEN Added comment: PMID: 36477332 identified de novo heterozygous missense variants in CLDN5 in fifteen unrelated patients who presented with a shared constellation of features including developmental delay, seizures (primarily infantile onset focal epilepsy), microcephaly and a recognizable pattern of pontine atrophy and brain calcifications. Sources: Literature |
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| Intellectual disability - microarray and sequencing v5.150 | PRKACB | Arina Puzriakova Phenotypes for gene: PRKACB were changed from Postaxial hand polydactyly; Postaxial foot polydactyly; Common atrium; Atrioventricular canal defect; Narrow chest; Abnormality of the teeth; Intellectual disability to Cardioacrofacial dysplasia 2, OMIM:619143 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v5.107 | ITPR1 |
Tracy Lester edited their review of gene: ITPR1: Added comment: PMID:29925855 - All 7 EOA patients with ITPR1 de novo variants (3 from cohort #1; 4 from cohort #2) presented with infantile onset cerebellar ataxia starting before the age of 2 years, including delayed motor milestones (Table 2). Cognitive deficits of variable degree were observed in 3 out of 4 patients where this information was available, reaching from only mild dyscalculia (P2) to severe intellectual disability with a speech vocabulary of only a few words (P7 at age 12 years). In contrast, patient P1 showed normal intelligence with an IQ of 97. PMID:27108797 - Here, we report that both recessive and dominant ITPR1 mutations cause Gillespie syndrome. ITPR1 is a predominant isoform in the brain among the three types of ITPRs and is strongly expressed in cerebellar Purkinje cells.31 Mice with complete homozygosity for Itpr1 ablation suffer from severe epilepsy and ataxia and die either in utero or before weaning.32 Consistently, ITPR1 mutations have been reported to cause cerebellar diseases including late-onset spinocerebellar ataxia type 15 (SCA15 [MIM: 606658]),33 congenital nonprogressive spinocerebellar ataxia and mild cognitive impairment (SCA29 [MIM: 117360]),34 infantile-onset cerebellar ataxia with mild cognitive deficit,35 and childhood-onset ataxic cerebellar palsy with moderate intellectual disability36 (see ITPR1 schematic diagram in Figure 3A). Affected individuals had similar iris anomalies and neonatal ataxia with progressive cerebellar atrophy (Figure 2). Moderate to severe intellectual disabilities were noted in the three individuals with recessive mutations (F1:II1, F2:II1, and F3:II1; Table 1). In contrast, the affected individual F4:II1 aged 18 years and harboring the de novo c.7687_7689del mutation was reported to have normal intelligence (Table 1). As de novo variants are associated with ID/DD the inheritance should be updated to be BOTH AD and AR.; Set current diagnostic: yes |
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| Intellectual disability - microarray and sequencing v5.70 | INTS11 |
Achchuthan Shanmugasundram changed review comment from: PMID:37054711 reported ten unrelated families with biallelic variants in INTS11 gene and they present with intellectual disability, global developmental and language delay, impaired motor development, and brain atrophy. Functional studies in Drosophila showed that dIntS11 (fly ortholog of INTS11) is essential and expressed in the central nervous systems in a subset of neurons and most glia in larval and adult stages. In addition, genes with two variants (p.Arg17Leu and p.His414Tyr) fail to rescue the lethality of null mutants in the Drosophila model, indicating that they are strong loss-of-function variants. The other five variants (p.Gly55Ser, p.Leu138Phe, p.Lys396Glu, p.Val517Met and p.Ile553Glu) rescue lethality but cause a shortened lifespan and bang sensitivity and affect locomotor activity, indicating that they are partial loss-of-function variants. Sources: Literature; to: PMID:37054711 reported ten unrelated families with biallelic variants in INTS11 gene and they present with intellectual disability, global developmental and language delay, impaired motor development, and brain atrophy. Functional studies in Drosophila showed that dIntS11 (fly ortholog of INTS11) is essential and expressed in the central nervous systems in a subset of neurons and most glia in larval and adult stages. In addition, genes with two variants (p.Arg17Leu and p.His414Tyr) fail to rescue the lethality of null mutants in the Drosophila model, indicating that they are strong loss-of-function variants. The other five variants (p.Gly55Ser, p.Leu138Phe, p.Lys396Glu, p.Val517Met and p.Ile553Glu) rescue lethality but cause a shortened lifespan and bang sensitivity and affect locomotor activity, indicating that they are partial loss-of-function variants. This gene has not yet been associated with relevant phenotypes in OMIM or in Gene2Phenotype. Sources: Literature |
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| Intellectual disability - microarray and sequencing v5.68 | INTS11 |
Achchuthan Shanmugasundram gene: INTS11 was added gene: INTS11 was added to Intellectual disability - microarray and sequencing. Sources: Literature Mode of inheritance for gene: INTS11 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: INTS11 were set to 37054711 Phenotypes for gene: INTS11 were set to intellectual disability, MONDO:0001071 Review for gene: INTS11 was set to GREEN Added comment: PMID:37054711 reported ten unrelated families with biallelic variants in INTS11 gene and they present with intellectual disability, global developmental and language delay, impaired motor development, and brain atrophy. Functional studies in Drosophila showed that dIntS11 (fly ortholog of INTS11) is essential and expressed in the central nervous systems in a subset of neurons and most glia in larval and adult stages. In addition, genes with two variants (p.Arg17Leu and p.His414Tyr) fail to rescue the lethality of null mutants in the Drosophila model, indicating that they are strong loss-of-function variants. The other five variants (p.Gly55Ser, p.Leu138Phe, p.Lys396Glu, p.Val517Met and p.Ile553Glu) rescue lethality but cause a shortened lifespan and bang sensitivity and affect locomotor activity, indicating that they are partial loss-of-function variants. Sources: Literature |
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| Intellectual disability - microarray and sequencing v5.5 | ARF1 | Achchuthan Shanmugasundram Added comment: Comment on publications: PMID:36345169 reported a paediatric patient identified with a monoallelic de novo missense variant (c.296 G > A; p.R99H) in the ARF1 gene, associated with developmental delay, hypotonia, intellectual disability and motor stereotypies. This patient did not exhibit periventricular heterotopias previously observed in other patients with ARF1 variants (including p.R99H). Functional analysis shows that the pathogenetic mechanism of the R99H-ARF1 variant involves constitutive activation with resultant Golgi and endosomal alterations. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v5.5 | ARF1 | Achchuthan Shanmugasundram Added comment: Comment on publications: PMID:36345169 reported a paediatric patient identified with a monoallelic de novo missense variant (c.296 G > A; p.R99H) in the ARF1 gene, associated with developmental delay, hypotonia, intellectual disability and motor stereotypies. This patient did not exhibit periventricular heterotopias previously observed in other patients with ARF1 variants (including p.R99H). Functional analysis shows that the pathogenetic mechanism of the R99H-ARF1 variant involves constitutive activation with resultant Golgi and endosomal alterations. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v5.4 | ARF1 | Achchuthan Shanmugasundram Added comment: Comment on publications: PMID:36345169 reported a paediatric patient identified with a monoallelic de novo missense variant (c.296 G > A; p.R99H) in the ARF1 gene, associated with developmental delay, hypotonia, intellectual disability and motor stereotypies. This patient did not exhibit periventricular heterotopias previously observed in other patients with ARF1 variants (including p.R99H). Functional analysis shows that the pathogenetic mechanism of the R99H-ARF1 variant involves constitutive activation with resultant Golgi and endosomal alterations. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v5.4 | ARF1 | Achchuthan Shanmugasundram Added comment: Comment on publications: PMID:36345169 reported a paediatric patient identified with a monoallelic de novo missense variant (c.296 G > A; p.R99H) in the ARF1 gene, associated with developmental delay, hypotonia, intellectual disability and motor stereotypies. This patient did not exhibit periventricular heterotopias previously observed in other patients with ARF1 variants (including p.R99H). Functional analysis shows that the pathogenetic mechanism of the R99H-ARF1 variant involves constitutive activation with resultant Golgi and endosomal alterations. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v4.90 | EMC1 | Achchuthan Shanmugasundram Phenotypes for gene: EMC1 were changed from Cerebellar atrophy, visual impairment, and psychomotor retardation, OMIM:616875 to Cerebellar atrophy, visual impairment, and psychomotor retardation, OMIM:616875 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v4.90 | EMC1 | Achchuthan Shanmugasundram Phenotypes for gene: EMC1 were changed from Cerebellar atrophy, visual impairment, and psychomotor retardation, OMIM:616875 to Cerebellar atrophy, visual impairment, and psychomotor retardation, OMIM:616875 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v4.90 | EMC1 | Achchuthan Shanmugasundram Phenotypes for gene: EMC1 were changed from Cerebellar atrophy, visual impairment, and psychomotor retardation, OMIM:616875 to Cerebellar atrophy, visual impairment, and psychomotor retardation, OMIM:616875 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v4.90 | EMC1 | Achchuthan Shanmugasundram Phenotypes for gene: EMC1 were changed from Cerebellar atrophy, visual impairment, and psychomotor retardation, OMIM:616875 to Cerebellar atrophy, visual impairment, and psychomotor retardation, OMIM:616875 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v4.89 | EMC1 | Achchuthan Shanmugasundram Phenotypes for gene: EMC1 were changed from Cerebellar atrophy, visual impairment, and psychomotor retardation, OMIM:616875 to Cerebellar atrophy, visual impairment, and psychomotor retardation, OMIM:616875 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v4.89 | EMC1 | Achchuthan Shanmugasundram Phenotypes for gene: EMC1 were changed from Cerebellar atrophy, visual impairment, and psychomotor retardation, OMIM:616875 to Cerebellar atrophy, visual impairment, and psychomotor retardation, OMIM:616875 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v4.89 | EMC1 | Achchuthan Shanmugasundram Phenotypes for gene: EMC1 were changed from Cerebellar atrophy, visual impairment, and psychomotor retardation, MIM 616875; Cerebellar atrophy, visual impairment, and psychomotor retardation, 616875 to Cerebellar atrophy, visual impairment, and psychomotor retardation, OMIM:616875 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v4.55 | ISCA-37408-Loss | Arina Puzriakova Phenotypes for Region: ISCA-37408-Loss were changed from PMID: 16963482 idiopathic intellectual disability including moderate to severe intellectual disability, autism/autistic features, microcephaly, structural brain anomalies including cortical dysplasia/pachygyria, renal anomalies (multicystic kidney, hydronephrosis), digital camptodactyly, visual impairment, strabismus, neuromotor deficits, communication and attention impairments, and a distinctive pattern of craniofacial features. Dysmorphic craniofacial features include progressive microcephaly, flat occiput, widened inner canthal distance, small palpebral fissures, ptosis, long and straight eyelashes, broad and high nasal root extending to a widened, prominent nasal tip with elongated, smooth philtrum, rounding of the upper vermillion border and everted lower lips. PMID: 18245392 A 32-year-old, mentally retarded male was referred to our centre for further clinical genetic analysis. He was born to non-consanguineous parents after 42 weeks gestation with a birth weight of 3500 g. He had a healthy older brother. In the neonatal period he was hypotonic and at 8 weeks of age he underwent surgery because of an inguinal hernia with removal of an atrophic right testis. His motor development was severely delayed with sitting at 3.5 years and walking at 5 years of age. Speech was poorly developed, characterised by the usage of only a few words. During infancy an optic nerve hypoplasia was diagnosed, and during childhood he frequently suffered from luxations of the patellae, which required surgery. At the age of 32 years his height is 163 cm (_3 SDS) and head circumference 52.5 cm (_2.5 SDS). He has a narrow receding forehead, widened inner canthal distance of 3.5 cm (90th centile), normal outer canthal distance of 8.5 cm (25th centile), telecanthus, short and down slanting palpebral fissures, epicanthal folds, ptosis, long, straight eyelashes, high nasal bridge, low set large ears, flat philtrum, small mouth with high, narrow palate and retrognathia. The thorax is broad with increased internipple distance and slight gynaecomastia. A recent renal ultrasound revealed multiple cysts in the left, dystrophic kidney and two uncomplicated cysts in the enlarged, right kidney. The patient has a normally sized phallus with absent right testis and small left testis. His hands show a simian crease right and tapering fingers with broad proximal interphalangeal joints. He shows sandal gaps on both flat feet with clinodactyly of the fourth and fifth toes (and more); 612513; PMID: 22579565 severe developmental delay, congenital microcephaly, intractable epilepsy, and renal anomalies, as well as a congenital choledochal cyst which has not been previously reported in other patients with this cytogenetic defect to Dysmorphic features, moderate to severe intellectual disability, microcephaly and renal anomalies | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v4.17 | KCNK3 |
Arina Puzriakova Added comment: Comment on list classification: Given the number of unrelated cases with a comparable phenotype, all shown to have variants that cluster near the X-gate and cause increased channel activation, this gene should be promoted to Green status at the next GMS panel update. The overall phenotype is likely most compatible with the Paediatric disorders super panel, and addition to the ID panel will ensure this genes' inclusion. |
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| Intellectual disability - microarray and sequencing v3.1757 | CTNNB1 | Arina Puzriakova Phenotypes for gene: CTNNB1 were changed from Mental retardation, autosomal dominant 19, 615075Colorectal cancer, somatic, 114500Pilomatricoma, somatic, 132600Ovarian cancer, somatic, 167000Hepatocellular carcinoma, somatic, 114550; MENTAL RETARDATION, AUTOSOMAL DOMINANT 19 to Neurodevelopmental disorder with spastic diplegia and visual defects, OMIM:615075 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.1733 | MTSS1L |
Arina Puzriakova gene: MTSS1L was added gene: MTSS1L was added to Intellectual disability. Sources: Literature new-gene-name, Q4_22_rating tags were added to gene: MTSS1L. Mode of inheritance for gene: MTSS1L was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: MTSS1L were set to 36067766 Phenotypes for gene: MTSS1L were set to Global developmental delay; Intellectual disability; Ophthalmological anomalies; Microcephaly; Mild facial dysmorphisms Review for gene: MTSS1L was set to GREEN Added comment: Huang et al. 2022 (PMID: 36067766) reported five unrelated individuals with the same heterozygous de novo variant (c.2011C>T; p.Arg671Trp) in MTSS2 (formally known as MTSS1L). Linkage analysis was not performed but given the variants arose de novo and the mixed ethnicity of the affected individuals (4 European, 1 Chinese) a founder effect can be ruled out. Subjects displayed a shared phenotype of GDD and/or ID, ophthalmological anomalies (most commonly nystagmus), microcephaly (primary in 2, relative in 3) and shared mild facial dysmorphisms. The single adult patient also presented with seizures and optic atrophy. Functional studies showed the variant leads to a decrease in mRNA level but does not impact protein levels of MTSS2. However, a Drosophila model demonstrated that loss of the fly ortholog results in defects in locomotor and visual functions which were rescued by human MTSS2 and only partially rescued by the MTSS2 c.2011C>T variant. Overexpression of the c.2011C>T variant caused similar phenotypes as the LoF mutant indicating a possible dominant-negative effect. Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.1702 | HEATR3 | Sarah Leigh Classified gene: HEATR3 as Amber List (moderate evidence) | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.1702 | HEATR3 | Sarah Leigh Added comment: Comment on list classification: The amber rating reflects that mild ID has been associated with HEATR3 variants. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.1702 | HEATR3 | Sarah Leigh Gene: heatr3 has been classified as Amber List (Moderate Evidence). | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.1685 | HEATR3 | Sarah Leigh reviewed gene: HEATR3: Rating: AMBER; Mode of pathogenicity: None; Publications: ; Phenotypes: ; Mode of inheritance: None | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.1685 | HEATR3 | Sarah Leigh Classified gene: HEATR3 as Amber List (moderate evidence) | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.1685 | HEATR3 | Sarah Leigh Gene: heatr3 has been classified as Amber List (Moderate Evidence). | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.1656 | TAF8 |
Arina Puzriakova Added comment: Comment on list classification: New gene added by Jana Jezkova. There is sufficient evidence to promote this gene to Green at the next GMS panel update. TAF8 is associated with a relevant phenotype in OMIM (MIM# 619972) but is not yet listed in G2P. 8 individuals from 5 families have been reported in literature (PMIDs: 29648665; 35759269). Four families from different ethnic backgrounds harboured the same c.781-1G>A homozygous variant while sequencing in a sib pair revealed different compound het splice variants (c.45+4A>G and c.489G>A) in the TAF8 gene. Patients presented with an overlapping phenotype including microcephaly (8/8), DD and ID (8/8), spasticity (7/8), and seizures (6/8). Brain MRI have shown hypoplastic corpus callosum, hypomyelination, enlarged ventricles in most subjects, and additionally generalised brain atrophy in two sibs. |
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| Intellectual disability - microarray and sequencing v3.1654 | TAF8 | Arina Puzriakova Phenotypes for gene: TAF8 were changed from severe developmental delay; feeding problems; microcephaly; growth retardation; spasticity; epilepsy to Neurodevelopmental disorder with severe motor impairment, absent language, cerebral hypomyelination, and brain atrophy, OMIM:619972 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.1649 | SLC38A3 | Catherine Snow Phenotypes for gene: SLC38A3 were changed from Infantile axial hypotonia; Global developmental delay; Intellectual disability; Seizures; Spasticity; Microcephaly; Cerebral atrophy; Cerebellar atrophy; Abnormality of the corpus callosum; Dysphagia; Constipation; Increased serum lactate; Hyperammonemia to Developmental and epileptic encephalopathy 102, 619881 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.1628 | PPFIBP1 |
Konstantinos Varvagiannis gene: PPFIBP1 was added gene: PPFIBP1 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: PPFIBP1 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: PPFIBP1 were set to 35830857; 30214071 Phenotypes for gene: PPFIBP1 were set to Global developmental delay; Intellectual disability; Microcephaly; Seizures; Abnormality of brain morphology; Abnormality of the cerebral white matter; Cerebral calcification; Abnormal cortical gyration; Hypertonia; Spastic tetraplegia; Generalized hypotonia; Small for gestational age; Growth delay; Failure to thrive; Feeding difficulties; abnormal heart morphology; Hearing abnormality; Cryptorchidism; Abnormality of vision Penetrance for gene: PPFIBP1 were set to Complete Review for gene: PPFIBP1 was set to GREEN Added comment: Consider inclusion with green rating in the ID, epilepsy as well as other likely relevant gene panels (microcephaly, white matter disorders, corpus callosum abnormalities, intracerebral calficication disorders, malformations of cortical development, hereditary spastic paraplegia, growth failure in early childhood, etc) based on the summary below. ---- Rosenhahn et al (2022 - PMID: 35830857) describe the phenotype of 16 individuals - belonging to 12 unrelated families - with biallelic PPFIBP1 pathogenic variants. Most (14/16) were born to consanguineous parents. One of these families was previously reported by Shaheen et al (2019 - PMID: 30214071) who first identified PPFIBP1 as a candidate gene for congenital microcephaly. In the current study, Rosenhahn also identified a fetus homozygous for a missense variant and similar features. All individuals presented global DD/ID (16/16 - in 15 cases profound/severe) and epilepsy (16/16 - onset 1d-4y / median 2m - focal seizures in 11/16, epileptic spams in 7/16, generalized onset in 7/16, myoclonic in 6/16 - drug-resistant : 13/16). Almost all (15/16) had microcephaly, commonly congenital (9/16) and progressive (11/16). Other neurological findings included hypertonia (10/16), spastic tetraplegia (6/16), hypotonia (5/16), dystonic movements (3/16) or nystagmus (4/16). Brain abnormalities were identified in all investigated with MRI and included leukoencephalopathy (11/14) mostly periventricular, abnormal cortex morphology (7/14 - polymicrogyria 1, increased cortical thickness 4, pachygyria 3), cortical atrophy, corpus callosum hypoplasia (7/14). Intracranial calcifications were identified in all (9/9) investigated with CT scan. Abnormal growth was reported for several (SGA in 9/16, FTT 8/16, short stature 7/16) often associated with feeding difficulties (7/16). Other features incl. abnormal hearing (4/16), congenital heart defects (7/16), ophthalmologic findings (8/16), undescended testes (3/10). There were no overlapping facial features. The fetus displayed similar features incl. SGA, microcephaly, intracranial calcifications. Investigations incl. exome/genome sequencing (singleton or trio) with Sanger for confirmation/segregation of variants where necessary. Variable previous investigations incl. metabolic screening, TORCH screening, chromosomal studies (CMA) are mentioned in the supplement and were non-diagnostic. Additional candidate variants were identified in few cases although cases with plausible dual diagnoses (e.g. ind14) were not included in the overall phenotypic description. 9 pLoF variants (nonsense, frameshift, 1 splicing) predicted to lead to NMD were identified. There were no functional studies performed. The missense variant c.2177G>T / p.Gly726Val (NM_003622.4) was predicted deleterious by in silico tools while the AA change causing severe steric problems upon modelling. PPFIBP1 encodes PPFIA-binding protein 1 also known as liprin-β1. As the authors discuss: The liprin family of proteins comprises liprins α1 to 4 and liprin β1 and β2 in mammals. Liprin β1 is known to homodimerize and heterodimerize with α-liprins. In fibroblast cultures liprins β1 and α1 colocalize to cell membrane and periphery of focal adhesions. Members of the liprin-α fam. are scaffold proteins playing a role in synapse formation/signaling and axonal transport. A ko model of the PPFIBP1 ortholog in C.elegans displayed abnormal locomotion behavior. In Drosophila, null-allele mutants resulted in altered axon outgrowth and synapse formation of R7 photoreceptors and reduced neuromuscular junction size (Refs provided in article). Using a PPFIBP1/hlb-1 ko C.elegans model the authors demonstrated defects in spontaneous and light-induced behavior. Sensitivity of the worms to an acetylcholinesterase inhibitor (aldicarb) was suggestive of a presynaptic defect. ---- There is currently no PPFIBP1 - associated phenotype in OMIM / G2P. SysNDD lists PPFIBP1 among the ID genes (limited evidence based on the 3 sibs reported by Shaheen et al, 2019 - PMID: 30214071). In PanelApp Australia the gene is listed with green rating for ID, epilepsy, microcephaly based on the medRxiv pre-print. Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.1612 | ATP6V0A1 | Sarah Leigh edited their review of gene: ATP6V0A1: Added comment: Not associated with a phenotype in OMIM, but as definitive Gen2Phen gene for ATP6V0A1-related developmental disorder (monoallelic). At least four variants have been reported as de novo heterozygous variants in 14 apparently unrelated cases, with intellectual disability (11/11 cases who could be assessed), epilepsy/EEG abnormalities (11/13 who could be assessed), microcephaly (6/12 cases who could be assessed), ataxia (6/13 cases who could be assessed) and various other phenotypic features (PMID: 34909687 (table 1) & 33833240). Six additional ATP6V0A1 variants were reported as biallelic in four apparently unrelated cases, who all had intellectual disability, epilepsy/EEG abnormalities plus cerebral and cerebellar atrophy / brain atrophy (PMID: 34909687 (table 1) & 33833240).; Changed rating: GREEN; Changed mode of inheritance: BOTH monoallelic and biallelic, autosomal or pseudoautosomal | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.1593 | ACO2 |
Sarah Leigh commented on gene: ACO2: New paper (34056600) describing ACO2 as a cause of autosomal dominant optic atrophy - update of inheritance needed. Tom Cullup (Great Ormond Street Hospital), 17 Feb 2022 |
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| Intellectual disability - microarray and sequencing v3.1580 | SRRM2 |
Konstantinos Varvagiannis changed review comment from: Recent report of 22 unrelated individuals with nonsense / frameshift variants or microdeletions of SRRM2 reported. DD was a universal feature, with ID present in some (16/20 - in all cases mild). Note possible 'overlap' with the study by Kaplanis et al / DDD study cited in the previous review by Prof. Z. Stark. The gene is not intolerant to missense variation (z-score of -6.28) and eventual contribution of missense variants is not known. While SRRM2 is known to encode a splicing factor promoting interaction between mRNA and the spliceosome catalytic machinery (discussed below) molecular and functional studies are required to characterize the pathogenesis of the disorder. There is currently no SRRM2-related phenotype in OMIM. SRRM2 is included in the DD panel of G2P [confidence : definitive, SRRM2-related developmental disorder (monoallelic), cited : Kaplanis et al / DDD]. In PanelApp Australia SRRM2 has amber rating in the ID panel (based on the study by Kaplanis et al / DDD). Consider inclusion with green rating (several individuals/families/variants - rather consistent phenotype) or amber rating (as for pathogenesis / also DD universal feature, ID observed in most but not all affected individuals, when present always mild). ----- Cuinat et al. (2022 - PMID: 35567594) report on 22 individuals with LoF variants in SRRM2. All subjects had DD (22/22) predominantly affecting language acquisition (16/19) while motor delay was less common. ID was present in 16/20 (in all cases mild) of the individuals with available neurocognitive evaluation. Some individuals displayed autistic features (9/22) although others had a friendly - in some cases excessively - sociable personality (8/22). Other features included hypotonia in some, growth abnormalities (12/22 overweight, 7/22 with obesity, 4/22 tall stature). Morphological features incl. facial (20/22 - e.g. deep-set eyes, bulbous nasal tip or smooth philtrum) or small hands and feet (6/22) were also reported. Visceral / skeletal abnormalities were uncommon. SRRM2 encodes serine/arginine repetitive matrix protein 2 (or SRm300), a nuclear ubiquitous protein forming a complex with the protein encoded by SRRM1 (SRm160). As the authors summarize this complex is one of the main catalytic components of the spliceosome having a role in pre-mRNA maturation. 12 subjects harbored frameshift variants, 8 nonsense while 2 further ones had microdeletions (66-270kb) spanning - but not limited to - SRRM2 (other genes not predicted to be haploinsufficient). The gene has a pLI in gnomAD of 1 (o/e = 0.06) while it appears to be tolerant to missense variation (z-score of -6.28 / o/e = 1.43). With the exception of the 2 subjects harboring a microdeletion, all were investigated with singleton/trio ES with no other candidate variants. Variants occurred de novo in 19/22. Mosaicism (in an asymptomatic parent) was suspected based on the reads in one case. One individual had inherited the variant (parent with DD). Segregation analyses was not possible in one case. While one variant lied in ex2 (of 15) all others were in the large ex11 (encoding ~2000 of the 2752 total residues based on the schema provided / NM_016333.4), all predicted to lead to NMD. There are no studies for pathogenesis of the disorder or the underlying effect of variants. Animal models not discussed. The authors do a comparison with other 'spliceosomopathies', e.g. due to variants in SF3B4 or EFTUD2, where DD/ID can be a feature although these disorders have also prominent skeletal features. Previously, as the authors note, the study by Kaplanis et al (2020 - PMID: 33057194) integrating exome sequence data from ~31,000 parent-offspring trios of individuals with developmental disorders had identified SRRM2 among 28 genes significantly enriched in LoF variants. [ The present study possibly includes individuals from the aforementioned cohort, e.g. from Radboudumc ].; to: Recent report of 22 unrelated individuals with nonsense / frameshift variants or microdeletions of SRRM2. DD was a universal feature, with ID present in some affected individuals (16/20 - in all cases mild). Note possible 'overlap' with the study by Kaplanis et al / DDD study cited in the previous review by Prof. Z. Stark. The gene is not intolerant to missense variation (z-score of -6.28) and eventual contribution of missense variants is not known. While SRRM2 is known to encode a splicing factor promoting interaction between mRNA and the spliceosome catalytic machinery (discussed below) molecular and functional studies are required to characterize the pathogenesis of the disorder. There is currently no SRRM2-related phenotype in OMIM. SRRM2 is included in the DD panel of G2P [confidence : definitive, SRRM2-related developmental disorder (monoallelic), cited : Kaplanis et al / DDD]. In PanelApp Australia SRRM2 has amber rating in the ID panel (based on the study by Kaplanis et al / DDD). Consider inclusion with green rating (several individuals/families/variants - rather consistent phenotype) or amber rating (as for pathogenesis / also DD universal feature, ID observed in most but not all affected individuals, when present always mild). ----- Cuinat et al. (2022 - PMID: 35567594) report on 22 individuals with LoF variants in SRRM2. All subjects had DD (22/22) predominantly affecting language acquisition (16/19) while motor delay was less common. ID was present in 16/20 (in all cases mild) of the individuals with available neurocognitive evaluation. Some individuals displayed autistic features (9/22) although others had a friendly - in some cases excessively - sociable personality (8/22). Other features included hypotonia in some, growth abnormalities (12/22 overweight, 7/22 with obesity, 4/22 tall stature). Morphological features incl. facial (20/22 - e.g. deep-set eyes, bulbous nasal tip or smooth philtrum) or small hands and feet (6/22) were also reported. Visceral / skeletal abnormalities were uncommon. SRRM2 encodes serine/arginine repetitive matrix protein 2 (or SRm300), a nuclear ubiquitous protein forming a complex with the protein encoded by SRRM1 (SRm160). As the authors summarize this complex is one of the main catalytic components of the spliceosome having a role in pre-mRNA maturation. 12 subjects harbored frameshift variants, 8 nonsense while 2 further ones had microdeletions (66-270kb) spanning - but not limited to - SRRM2 (other genes not predicted to be haploinsufficient). The gene has a pLI in gnomAD of 1 (o/e = 0.06) while it appears to be tolerant to missense variation (z-score of -6.28 / o/e = 1.43). With the exception of the 2 subjects harboring a microdeletion, all were investigated with singleton/trio ES with no other candidate variants. Variants occurred de novo in 19/22. Mosaicism (in an asymptomatic parent) was suspected based on the reads in one case. One individual had inherited the variant (parent with DD). Segregation analyses was not possible in one case. While one variant lied in ex2 (of 15) all others were in the large ex11 (encoding ~2000 of the 2752 total residues based on the schema provided / NM_016333.4), all predicted to lead to NMD. There are no studies for pathogenesis of the disorder or the underlying effect of variants. Animal models not discussed. The authors do a comparison with other 'spliceosomopathies', e.g. due to variants in SF3B4 or EFTUD2, where DD/ID can be a feature although these disorders have also prominent skeletal features. Previously, as the authors note, the study by Kaplanis et al (2020 - PMID: 33057194) integrating exome sequence data from ~31,000 parent-offspring trios of individuals with developmental disorders had identified SRRM2 among 28 genes significantly enriched in LoF variants. [ The present study possibly includes individuals from the aforementioned cohort, e.g. from Radboudumc ]. |
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| Intellectual disability - microarray and sequencing v3.1580 | DROSHA |
Konstantinos Varvagiannis gene: DROSHA was added gene: DROSHA was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: DROSHA was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: DROSHA were set to 35405010 Phenotypes for gene: DROSHA were set to Global developmental delay; Intellectual disability; Seizures; Cerebral white matter atrophy; Abnormality of the corpus callosum; Abnormality of movement; Stereotypic behavior; Abnormality of head or neck; Short foot Penetrance for gene: DROSHA were set to unknown Mode of pathogenicity for gene: DROSHA was set to Loss-of-function variants (as defined in pop up message) DO NOT cause this phenotype - please provide details in the comments Review for gene: DROSHA was set to AMBER Added comment: Profound DD, ID and seizures have been reported in 2 unrelated subjects with de novo missense variants. The gene has a role in miRNA biogenesis. Both variants described have been shown to have effect on DROSHA's function in Drosophila / C. elegans (partial loss-of-function vs possibility of antimorphic effect discussed || in gnomAD several individuals with LoF alleles / Z=3.98 – pLI : 0.09). There is currently no DROSHA-related phenotype in OMIM, G2P, SysNDD. In PanelApp Australia the gene has amber rating in genetic epilepsy and microcephaly panels (not currently included in the ID one). Consider inclusion in the current panel with amber rating. Also consider inclusion in other possibly relevant panels (given postnatal microcephaly, abn. corpus callosum, progressive white matter atrophy, etc) [ NOT added ] ----- Barish, Senturk, Schoch et al (2022 - PMID: 35405010) describe the phenotype of 2 unrelated individuals with de novo missense DROSHA variants. Features included generalized hypotonia, postnatal microcephaly (-2,6 and -6 SD), feeding difficulties, profound DD and ID, seizures, abnormal movements (choreoathetosis / stereotypic movements), variable respiratory symptoms (in one case episodes of hyperventilation/apnea), cardiovascular or skeletal findings. Brain MRI demonstrated white matter atrophy and thin corpus callosum in both. Brachycephaly with broad face as well as short feet were also among the shared features. Both were investigated by trio ES/GS which were otherwise non diagnostic and without other candidate variants. The 1st individual harbored a de novo htz missense DROSHA variant (c.3656A>G/p.Asp1219Gly) while the 2nd subject had another missense variant (c.4024C>T/p.Arg1342Trp) [NM_013235.4] confirmed by Sanger seq. DROSHA (on 5p13.3) encodes a ribonuclease, subunit of the microprocessor complex, involved in miRNA biogenesis. Specifically, miRNAs are transcribed as part of pri-miRNAs (primary-miRNAs) which are cleaved to pre-miRNAs (precursor-miRNAs) in the nucleus by DROSHA (and its partner DGCR8 or Pasha) and then exported to the cytoplasm for further processing. Cleavage of pre-miRNAs by DICER1 generates mature miRNAs subsequently loaded to the RISC (RNA-induced silencing) complex which uses miRNA as template for recognition and cleavage of complementary mRNA with RNAse. As the authors discuss, miRNA defects have a well-established role in development of model organisms e.g. (several Refs. provided): - in C. elegans miRNA mutants causing lethality, developmental arrest and heterochronicity - in Drosophila playing a role in the development of ovary, eye, nervous system etc. - in mice mRNAs play a role in BMP and TGF-beta signaling while neuronal loss of miRNA processing leads to neurodegeneration/anatomical defects. Feingold syndrome 2 is the single Mendelian disease associated to date with miRNAs, through deletion of a cluster containing 6 MIR genes. miRNA dysregulation is also observed in Rett syndrome - and DROSHA implicated in the pathogenesis of the syndrome - as MECP2 and FOXG1 are cofactors of the microprocessor complex regulating processing of miRNA. One of the individuals here reported had a clinical diagnosis of Rett spectrum while both had overlapping features with Rett s. Studies of DROSHA-dependent miRNAs in fibroblasts from one individual revealed significantly altered expression of mature miRNA (e.g. increased miR98, a miRNA with reduced expression in studies of somatic DROSHA variants) although this was not likely due to processing errors (given only a modest decrease of precursor miRNAs). Previous studies have demonstrated that drosha (the Drosophila ortholog) null mutants die during post-embryonic development with 100% lethality before adulthood (3rd instar larval stage/beginning of pupariation). Mosaic flies with mutant eyes are small-eyed, while viable hypomorphic alleles display synaptic transmission defects (several Refs provided). Here, homozygous flies for null alleles died at the end of 3rd instar larval stage/beginning of pupariation, while loss of drosha resulted in lack of imaginal disc tissue (which surrounds the larval brain) and severely reduced brain size, the latter similar to the microcephaly phenotype. [To the best of my understanding] introduction of a mutated genomic rescue construct (carrying similar substitutions as those observed in human subjects) in eye-specific drosha null (W1123X) flies was partially able to rescue eye/head size for wt or Asp1219Gly (human:Asp1084Gly) suggesting that the latter is a partial LoF allele. Arg1210Trp (corresponding to human Arg1342Trp) was able to rescue the eye phenotype and was not damaging to the function in the specific assay. Drosha expression levels were similar for genomic rescue flies either for wt or for the Asp-Gly variant suggesting that the effect was not due to expression levels (but rather function). Expression of mature miRNAs known to be regulated by Drosha were not affected when comparing wildtype larvae with genomic construct for wt or Asp1084Gly. Upon expression of human cDNA using GAL4/UAS system in drosha mutant (null) eye clones, the reference partially rescued the eye size defect, Asp-Gly behaved as partial loss-of-function allele (~50% function compared to ref), while the Arg-Trp variant was shown to behave as a weaker loss-of-function allele. The authors generated eye-specific drosha mutant clones to study the aging adult eye using ERG recordings. While null mutants display almost no response to light (7- and 20-day old flies), wt genomic rescue was shown to rescue ERG responses, Asp-Gly variant had significant defects (at both 7 and 20 days) and the Arg-Trp had defects approaching statistical significance only at the age of 20 days. Overall these data suggested that Arg-Trp had less severe effect compared to Asp-Gly (as above) while both variants led to progressive neuronal dysfunction. Using CRISPR/Cas9 the authors generated C.elegans knock-ins for a variant analogous to the Asp1219Gly human one. Homozygous animals were inviable at larval stages, displayed a heterochronic phenotype (heterochronicity : development of cells or tissues at an abnormal time relative to other unaffected events in an organism / miRNAs are known to be involved in the heterochronic gene pathway) while this variant was deleterious to the Drosha's ability to process miRNAs. Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.1561 | CDK9 |
Konstantinos Varvagiannis changed review comment from: There are 4 studies reporting on the phenotype associated with biallelic CDK9 pathogenic variants. DD and ID are part of the phenotype which appears to be relatively consistent. CDK9 encodes Cyclin-dependent kinase 9. There are 4 missense variants reported to date - one of which recurrent (NM_001261.3:c.673C>T / p.Arg225Cys) - with studies for 3 variants suggesting a LoF effect (loss of kinase activity) [Ref4]. Animal models also provide some supporting evidence [discussed Ref4]. Consider inclusion in the current panel (probably with green rating) as well as other possibly relevant ones. Details provided below. [1]----- Shaheen et al (2016 - PMID: 26633546) studied patients with apparently novel phenotypes with positive family history consistent with AR inheritance mode due to consanguinity. After autozygome analysis the authors determined the shared autozygome (ROH >1 Mb / Axiom SNP Chip) in families with multiple affected individuals. This analysis was followed by whole exome/genome sequencing. Using this approach, they managed to map the phenotype of interest to a single novel locus in some families, which was also the case in a large consanguineous family with 2 similarly affected cousins (11DG0424, 11DG1630). Within a 20 Mb region of homozygosity, followed by WES in a single affected individual and Sanger confirmation with compatible segregation studies in parents and 10 unaffected sibs, the authors identified a homozygous CDK9 missense SNV (NM_001261.3:c.673C>T / p.Arg225Cys) responsible for this phenotype. In silico predictions were concordant in favor of a deleterious effect. Features (detailed in the suppl.) included global DD (2/2), severe ID (1/1), cerebral and (mild) cerebellar atrophy (2/2), microcephaly (2/2), ocular anomalies (2/2, coloboma in 2/2, congenital cataract 2/2, etc), heart defects (2/2, PDA in both, ASD), variable genitourinary anomalies (2/2 incl. hydronephrosis, VUR reflux/recurrent UTIs, kidney atrophy, abn. genitalia in 1), abnormalities of the limbs (2/2, bilateral talipes equinovarus : 2/2) or the skeleton (1/2 - butterfly vertebrae). One was reported to have some degree of growth delay (<10th centile for length, <5th for weight and OFC). There was no hearing defect reported (large ears in 1/2). Overall, the authors used the term CHARGE-like phenotype. [2]----- Maddirevula et al (2019 - PMID: 30237576) performed autozygome and exome analysis of individuals with suspected Mendelian disorders. They reported 3 individuals (18DG0161, 18DG0162, 18DG0165) born to 3 different consanguineous families (information in fig2) from Qatar, homozygous for CDK9 p.Arg225Cys. All presented a CHARGE-like phenotype with features ophtalmologic findings (3/3 - abnormal ERG in one, congenital cataracts the other, visual impairment in the 3rd, though NO evidence of coloboma in at least two), heart defect (2/3 had VSD), choanal atresia (3/3), retarded growth/FTT (1/3) or global DD (3/3 - in suppl. table 1), (genito)urinary anomalies (1/3 - dysplastic atrophic kidney) or ear anomalies (3/3 - preauricular tags 2/3, bilateral deafness 1/3, bilat.ossicular anomalies 1/3). Other features incl. epilepsy (2/3), brain MRI abnormalities (2/3), facial asymmetry in one, vertebral segmentation defect in 1/3. [3]----- Hu et al (2019 - PMID: 29302074) performed WES/WGS in 404 consanguineous families from Iran, having 2 or more offspring with ID. In this context they reported 2 females and a male (III:1,4,3 belonging to fam. M9100018 - details in suppl. text) born to first cousin parents from Iran. Features included DD (3/3 - walking at 3y, words at 4y), moderate ID (3/3 - WAIS-IV IQ of 40-43), short stature (3/3 below 3rd %le). Vision and hearing were normal. All three were homozygous for a missense SNV (NM_001261:c.280C>T, p.Arg94Cys) which was ultrarare in ExAC, with severa in silico tools in favor of a deleterious effect. The authors commented that CDK9 is the catalytic core of transcription elongation factor p-TEFb essential for transcription elongation of numerous genes, Cdk9/Cyclin T1 complex may participate in neuronal differentiation, CDK9-cyclinK in maintenance of genomic integrity, with the protein encoded also interacted with AF4/FMR2. In addition the gene was commented to have ubiquitous expression with high protein expression in glial and neuronal cells of the cortex (based on Uniprot and Human Protein Atlas). [4]----- Nishina et al (2021 - PMID: 33640901) described an 8 y.o. male with facial asymmetry, ear/hearing anomalies (microtia, preauricular tags, bilateral hearing loss), ocular/vision anomalies (blepharophimosis, lacrimal obstruction, eyelid dermoids, duane-like anomaly, congenital cataracts, retinal dystrophy), cleft lip and palate, abnormalities of the limbs (finger contractures with associated absence of creases, cutaneous syndactyly, etc). Other features included cardiac dysrhythmia and undescended testes. Development was delayed with associated ID (walking 3y, words 7y, at 10y: could count to 20, 4 word sentences). There was no evidence of coloboma or choanal atresia. Trio exome sequencing revealed that the child was compound htz for 2 missense SNVs (NM_001261.3:c.862G>A / p.Ala288Thr and c.907C>T /p.Arg303Cys) with Sanger confirmation. These were ultrarare/not present in gnomAD. Both lied in the protein kinase catalytic domain of CDK9, with high conservation across different species and in silico predictions in favor of deleterious effect. In vitro studies in HEK293 cells demonstrated that the kinase activity for both variants was significantly reduced compared to wt. Kinase activity was also reduced for the Arg225Cys variant (reported in Refs 1 & 2). The authors briefly discuss evidence from zebrafish (regulates larval morphogenesis incl. brain, heart, eye, blood vessels) and mouse models. In the latter complete LoF is lethal while heterozygous LoF is associated with abnormal morphology of heart, skin and epididymis (PMIDs cited by the authors : 27715402, 30100824). Sources: Literature; to: There are 4 studies reporting on the phenotype associated with biallelic CDK9 pathogenic variants. DD and ID are part of the phenotype which appears to be relatively consistent. CDK9 encodes Cyclin-dependent kinase 9. There are 4 missense variants reported to date - one of which recurrent (NM_001261.3:c.673C>T / p.Arg225Cys) - with studies for 3 variants suggesting a LoF effect (loss of kinase activity) [Ref4]. Animal models also provide some supporting evidence [discussed Ref4]. Consider inclusion in the current panel (probably with green rating) as well as other possibly relevant ones. Details provided below. [1]----- Shaheen et al (2016 - PMID: 26633546) studied patients with apparently novel phenotypes with positive family history consistent with AR inheritance due to consanguinity. Using autozygome analysis the authors determined the shared autozygome (ROH >1 Mb / Axiom SNP Chip) in families with multiple affected individuals. This analysis was followed by whole exome/genome sequencing. Using this approach, they managed to map the phenotype of interest to a single novel locus in some families, which was also the case in a large consanguineous family with 2 similarly affected cousins (11DG0424, 11DG1630). Within a 20 Mb region of homozygosity, followed by WES in a single affected individual and Sanger confirmation with compatible segregation studies in parents and 10 unaffected sibs, the authors identified a homozygous CDK9 missense SNV (NM_001261.3:c.673C>T / p.Arg225Cys) responsible for this phenotype. In silico predictions were concordant in favor of a deleterious effect. Features (detailed in the suppl.) included global DD (2/2), severe ID (1/1), cerebral and (mild) cerebellar atrophy (2/2), microcephaly (2/2), ocular anomalies (2/2, coloboma in 2/2, congenital cataract 2/2, etc), heart defects (2/2, PDA in both, ASD), variable genitourinary anomalies (2/2 incl. hydronephrosis, VUR/recurrent UTIs, kidney atrophy, abn. genitalia in 1), abnormalities of the limbs (2/2, bilateral talipes equinovarus : 2/2) or the skeleton (1/2 - butterfly vertebrae). One was reported to have some degree of growth delay (<10th centile for length, <5th for weight and OFC). There was no hearing defect reported (large ears in one case). Overall, the authors used the term CHARGE-like for this phenotype. [2]----- Maddirevula et al (2019 - PMID: 30237576) performed autozygome and exome analysis of individuals with suspected Mendelian disorders. They reported 3 individuals (18DG0161, 18DG0162, 18DG0165) born to 3 different consanguineous families (information in fig2) from Qatar, homozygous for CDK9 p.Arg225Cys. All presented a CHARGE-like phenotype with ophthalmologic findings (3/3 - abnormal ERG in one, congenital cataracts the other, visual impairment in the 3rd, though NO evidence of coloboma in at least two of them), heart defect (2/3 with VSD), choanal atresia (3/3), retarded growth/FTT (1/3) or global DD (3/3 - in suppl. table 1), (genito)urinary anomalies (1/3 - dysplastic atrophic kidney) or ear anomalies (3/3 - preauricular tags in 2/3, bilateral deafness 1/3, bilateral ossicular anomalies 1/3). Other features incl. epilepsy (2/3), brain MRI abnormalities (2/3), facial asymmetry in one, vertebral segmentation defect in 1/3. [3]----- Hu et al (2019 - PMID: 29302074) performed WES/WGS in 404 consanguineous families from Iran, having 2 or more offspring with ID. In this context they reported 2 females and a male (III:1,4,3 belonging to fam. M9100018 | suppl. text) born to first cousin parents from Iran. Features included DD (3/3 - walking at 3y, words at 4y), moderate ID (3/3 - WAIS-IV IQ of 40-43), short stature (3/3 below 3rd %le). Vision and hearing were normal. All three were homozygous for a missense SNV (NM_001261:c.280C>T, p.Arg94Cys) which was ultrarare in ExAC, with several in silico tools in favor of a deleterious effect. The authors commented that CDK9 is the catalytic core of transcription elongation factor p-TEFb essential for transcription elongation of numerous genes, Cdk9/Cyclin T1 complex may participate in neuronal differentiation, CDK9-cyclinK in maintenance of genomic integrity, with the protein encoded also interacting with AF4/FMR2. In addition the gene was commented to have ubiquitous expression with high protein expression in glial and neuronal cells of the cortex (based on Uniprot and Human Protein Atlas). [4]----- Nishina et al (2021 - PMID: 33640901) described an 8 y.o. male with facial asymmetry, ear/hearing anomalies (microtia, preauricular tags, bilateral hearing loss), ocular/vision anomalies (blepharophimosis, lacrimal obstruction, eyelid dermoids, duane-like anomaly, congenital cataracts, retinal dystrophy), cleft lip and palate, abnormalities of the limbs (finger contractures with associated absence of creases, cutaneous syndactyly, etc). Other features included cardiac dysrhythmia and undescended testes. Development was delayed with ID (walking 3y, words 7y, at 10y: could count to 20, 4 word sentences). There was no evidence of coloboma or choanal atresia. Trio exome revealed that the child was compound htz for 2 missense SNVs (NM_001261.3:c.862G>A / p.Ala288Thr and c.907C>T /p.Arg303Cys) with Sanger confirmation. These were ultrarare/not present in gnomAD. Both lied in the protein kinase catalytic domain of CDK9, with high conservation across different species and in silico predictions in favor of deleterious effect. In vitro studies in HEK293 cells demonstrated that the kinase activity for both variants was significantly reduced compared to wt. Kinase activity was also reduced for the Arg225Cys variant (reported in Refs 1 & 2). The authors briefly discuss evidence from zebrafish (regulates larval morphogenesis incl. brain, heart, eye, blood vessels) and mouse models. In the latter complete LoF is lethal while heterozygous LoF is associated with abnormal morphology of heart, skin and epididymis (PMIDs cited : 27715402, 30100824). Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.1561 | CDK9 |
Konstantinos Varvagiannis gene: CDK9 was added gene: CDK9 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: CDK9 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: CDK9 were set to 26633546; 30237576; 29302074; 33640901 Phenotypes for gene: CDK9 were set to Global developmental delay; Intellectual disability; Abnormality of vision; Congenital cataract; Iris coloboma; Abnormal heart morphology; Choanal atresia; Abnormality of the ear; Preauricular skin tag; Hearing impairment; Abnormality of the genitourinary system; Abnormality of limbs; Abnormality of the vertebrae; Abnormality of nervous system morphology; Seizures Penetrance for gene: CDK9 were set to Complete Review for gene: CDK9 was set to GREEN Added comment: There are 4 studies reporting on the phenotype associated with biallelic CDK9 pathogenic variants. DD and ID are part of the phenotype which appears to be relatively consistent. CDK9 encodes Cyclin-dependent kinase 9. There are 4 missense variants reported to date - one of which recurrent (NM_001261.3:c.673C>T / p.Arg225Cys) - with studies for 3 variants suggesting a LoF effect (loss of kinase activity) [Ref4]. Animal models also provide some supporting evidence [discussed Ref4]. Consider inclusion in the current panel (probably with green rating) as well as other possibly relevant ones. Details provided below. [1]----- Shaheen et al (2016 - PMID: 26633546) studied patients with apparently novel phenotypes with positive family history consistent with AR inheritance mode due to consanguinity. After autozygome analysis the authors determined the shared autozygome (ROH >1 Mb / Axiom SNP Chip) in families with multiple affected individuals. This analysis was followed by whole exome/genome sequencing. Using this approach, they managed to map the phenotype of interest to a single novel locus in some families, which was also the case in a large consanguineous family with 2 similarly affected cousins (11DG0424, 11DG1630). Within a 20 Mb region of homozygosity, followed by WES in a single affected individual and Sanger confirmation with compatible segregation studies in parents and 10 unaffected sibs, the authors identified a homozygous CDK9 missense SNV (NM_001261.3:c.673C>T / p.Arg225Cys) responsible for this phenotype. In silico predictions were concordant in favor of a deleterious effect. Features (detailed in the suppl.) included global DD (2/2), severe ID (1/1), cerebral and (mild) cerebellar atrophy (2/2), microcephaly (2/2), ocular anomalies (2/2, coloboma in 2/2, congenital cataract 2/2, etc), heart defects (2/2, PDA in both, ASD), variable genitourinary anomalies (2/2 incl. hydronephrosis, VUR reflux/recurrent UTIs, kidney atrophy, abn. genitalia in 1), abnormalities of the limbs (2/2, bilateral talipes equinovarus : 2/2) or the skeleton (1/2 - butterfly vertebrae). One was reported to have some degree of growth delay (<10th centile for length, <5th for weight and OFC). There was no hearing defect reported (large ears in 1/2). Overall, the authors used the term CHARGE-like phenotype. [2]----- Maddirevula et al (2019 - PMID: 30237576) performed autozygome and exome analysis of individuals with suspected Mendelian disorders. They reported 3 individuals (18DG0161, 18DG0162, 18DG0165) born to 3 different consanguineous families (information in fig2) from Qatar, homozygous for CDK9 p.Arg225Cys. All presented a CHARGE-like phenotype with features ophtalmologic findings (3/3 - abnormal ERG in one, congenital cataracts the other, visual impairment in the 3rd, though NO evidence of coloboma in at least two), heart defect (2/3 had VSD), choanal atresia (3/3), retarded growth/FTT (1/3) or global DD (3/3 - in suppl. table 1), (genito)urinary anomalies (1/3 - dysplastic atrophic kidney) or ear anomalies (3/3 - preauricular tags 2/3, bilateral deafness 1/3, bilat.ossicular anomalies 1/3). Other features incl. epilepsy (2/3), brain MRI abnormalities (2/3), facial asymmetry in one, vertebral segmentation defect in 1/3. [3]----- Hu et al (2019 - PMID: 29302074) performed WES/WGS in 404 consanguineous families from Iran, having 2 or more offspring with ID. In this context they reported 2 females and a male (III:1,4,3 belonging to fam. M9100018 - details in suppl. text) born to first cousin parents from Iran. Features included DD (3/3 - walking at 3y, words at 4y), moderate ID (3/3 - WAIS-IV IQ of 40-43), short stature (3/3 below 3rd %le). Vision and hearing were normal. All three were homozygous for a missense SNV (NM_001261:c.280C>T, p.Arg94Cys) which was ultrarare in ExAC, with severa in silico tools in favor of a deleterious effect. The authors commented that CDK9 is the catalytic core of transcription elongation factor p-TEFb essential for transcription elongation of numerous genes, Cdk9/Cyclin T1 complex may participate in neuronal differentiation, CDK9-cyclinK in maintenance of genomic integrity, with the protein encoded also interacted with AF4/FMR2. In addition the gene was commented to have ubiquitous expression with high protein expression in glial and neuronal cells of the cortex (based on Uniprot and Human Protein Atlas). [4]----- Nishina et al (2021 - PMID: 33640901) described an 8 y.o. male with facial asymmetry, ear/hearing anomalies (microtia, preauricular tags, bilateral hearing loss), ocular/vision anomalies (blepharophimosis, lacrimal obstruction, eyelid dermoids, duane-like anomaly, congenital cataracts, retinal dystrophy), cleft lip and palate, abnormalities of the limbs (finger contractures with associated absence of creases, cutaneous syndactyly, etc). Other features included cardiac dysrhythmia and undescended testes. Development was delayed with associated ID (walking 3y, words 7y, at 10y: could count to 20, 4 word sentences). There was no evidence of coloboma or choanal atresia. Trio exome sequencing revealed that the child was compound htz for 2 missense SNVs (NM_001261.3:c.862G>A / p.Ala288Thr and c.907C>T /p.Arg303Cys) with Sanger confirmation. These were ultrarare/not present in gnomAD. Both lied in the protein kinase catalytic domain of CDK9, with high conservation across different species and in silico predictions in favor of deleterious effect. In vitro studies in HEK293 cells demonstrated that the kinase activity for both variants was significantly reduced compared to wt. Kinase activity was also reduced for the Arg225Cys variant (reported in Refs 1 & 2). The authors briefly discuss evidence from zebrafish (regulates larval morphogenesis incl. brain, heart, eye, blood vessels) and mouse models. In the latter complete LoF is lethal while heterozygous LoF is associated with abnormal morphology of heart, skin and epididymis (PMIDs cited by the authors : 27715402, 30100824). Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.1559 | AFG3L2 | Arina Puzriakova Phenotypes for gene: AFG3L2 were changed from Spastic ataxia 5, autosomal recessive OMIM:614487; spastic ataxia 5 MONDO:0013776; Spinocerebellar ataxia 28 OMIM:610246; spinocerebellar ataxia type 28 MONDO:0012450 to Optic atrophy 12, OMIM:618977; Spinocerebellar ataxia 28, OMIM:610246; Spastic ataxia 5, autosomal recessive, OMIM:614487 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.1558 | SLC35B2 |
Konstantinos Varvagiannis gene: SLC35B2 was added gene: SLC35B2 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: SLC35B2 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: SLC35B2 were set to 35325049 Phenotypes for gene: SLC35B2 were set to Abnormality of the skeletal system; Short long bone; Short stature; Abnormality of epiphysis morphology; Scoliosis; Multiple joint dislocation; Global develpmental delay; Intellectual disability; CNS hypomyelination; Abnormality of the corpus callosum; Cerebral atrophy; Abnormality of the amniotic fluid Penetrance for gene: SLC35B2 were set to Complete Review for gene: SLC35B2 was set to AMBER Added comment: 2 unrelated individuals with biallelic SLC35B2 variants have been reported. DD and ID were part of the phenotype. There is currently no associated phenotype in OMIM/G2P/SysID. The gene has amber rating in the leukodystrophies panel of PanelApp Australia. Consider inclusion in the current panel (or other possibly relevant ones eg. for skeletal disorders, short stature, white matter disorders, corpus callosum, etc) with amber rating. --- Guasto et al (2022 - PMID:35325049) report 2 unrelated individuals with biallelic SLC35B2 variants. SLC35B2 encodes solute carrier family 35 (3'-phosphoadenosine 5'-phosphosulfate (PAPS) transporter), member B2. The protein is located in the Golgi membrane and serves as transporter of the activated nucleotide sulfate PAPS from the cytosol, where it is synthesized to the Golgi lumen. Another PAPS transporter is encoded by SLC35B3. In the Golgi apparatus PAPS serves as substrate of sulfotransferases for the addition sulfate to the covalently attached GAG chains of proteoglycans (PGs). The phenotype corresponded to a chondrodysplasia manifesting as severe pre- and postnatal growth retardation (height <-4 SD and -8 SD), early scoliosis, multiple joint dislocations (in one). There was severe DD affecting motor and expressive language development with associated ID. Brain imaging was suggestive of hypomyelinating leukodystrophy with thin corpus callosum and cerebral atrophy. One individual had a cleft palate in the context of Pierre Robin sequence. Both individuals were investigated with exome sequencing. The first individual - born to consanguineous parents - was homozygous for an in-frame del (NM_178148.3:c.1218_1220del, p.Leu407del) with Sanger sequencing confirming the variants, and heterozygosity in parents and 2 unaffected sibs. There was an initially identified hmz CUL7 variant (for 3M syndrome), which was not felt sufficient to explain the severity of the phenotype and notably ID. The 2nd proband was homozygous for a fs variant (c.1224_1225delAG / p.Arg408SerfsTer18 - leading to loss of the last 8 amino acids) occurring in the context of uniparental isodisomy [iUPD(6)] spanning the complete chr6 based on the exome data. Among the evidence presented for SLC35B2 and the variants : - SLC35B2 has high mRNA expression in fetal and adult mouse brain and other tissues. - Upon qPCR analysis of mRNA expression in human brain samples, the gene had expression across the brain (frontal lobe grey matter, subcortical frontal white matter/cerebellum). - High expression was shown upon analysis of mouse brain single cell RNA data (EMBL) in oligodendrocytes and microglial cells. - RT-PCR on mRNA from skin fibroblasts (both individuals) revealed significant decrease of SCL35B2 mRNA levels compared to controls. - Transfection of C-terminal c-myc tagged wt or mutant proteins in HEK293F cells, followed by western blotting did not reveal significant difference at the protein level. Wt SLC35B2 localized at the Golgi apparatus as suggested by colocalization with GM130 marker. The 2 variants however displayed only partial colocalization (/loss of localization specificity) with diffuse signal in the cell. - Chondroitin sulfate disaccharide sulfation was decreased upon HPLC disaccharide analysis in patient fibroblasts and bikunin (a circulating proteoglycan in blood) electrophoretic pattern in patient sera. - Disorders due to variants in genes implicated in proteoglycan biogenesis (e.g. XYLT1, B3GALT6, CHSY1) are associated with skeletal/connective tissue manifestations with DD/ID. - C-elegans model lacking pst-1 (SLC35B2 ortholog) provides support that the protein is required for migration, axonal guidance, and presynaptic development in a subset of neurons. - dsm-1 - the rat ortholog - is expressed in rat brain in D-serine and NMDA receptor rich regions. When expressed in Xenopus oocytes it accelerated the efflux of D-serine (a co-agonist for NMDA receptor). - Variants in other members of SLC superfamily (e.g. SLC17A5, SLC35A3, SLC29A3, SLC35A2) have been associated with brain-bone phenotypes. Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.1555 | DTYMK | Sarah Leigh Phenotypes for gene: DTYMK were changed from 31271740; 34918187; 35346037 to Global developmental delay; Intellectual disability; Microcephaly; Seizures; Global brain atrophy; Cardiorespiratory arrest | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.1554 | DTYMK | Sarah Leigh Publications for gene: DTYMK were set to Global developmental delay; Intellectual disability; Microcephaly; Seizures; Global brain atrophy; Cardiorespiratory arrest | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.1549 | HSPD1 | Arina Puzriakova Added comment: Comment on mode of inheritance: Should be updated from 'both mono- and biallelic' to 'biallelic' only at the next GMS panel update. Biallelic variants cause a paediatric-onset leukodystrophy (MIM# 612233) which can feature severe DD/ID in some cases (PMID: 18571143, 27405012), whereas monoallelic variants are associated with a pure adult-onset HSP (SPG13, MIM# 605280) which is not pertinent to this panel. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.1548 | PLEC | Arina Puzriakova Phenotypes for gene: PLEC were changed from Muscular dystrophy with epidermolysis bullosa simplex, 226670; Epidermolysis bullosa simplex, Ogna type, 131950; Epidermolysis bullosa simplex with pyloric atresia, 612138; Muscular dystrophy, limb-girdle, type 2Q, 613723 to Epidermolysis bullosa simplex 5D, generalized intermediate, autosomal recessive, OMIM:616487; Epidermolysis bullosa simplex 5A, Ogna type, OMIM:131950; Epidermolysis bullosa simplex 5B, with muscular dystrophy, OMIM:226670; Epidermolysis bullosa simplex 5C, with pyloric atresia, OMIM:612138; Muscular dystrophy, limb-girdle, autosomal recessive 17, OMIM:613723 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.1544 | DTYMK |
Konstantinos Varvagiannis gene: DTYMK was added gene: DTYMK was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: DTYMK was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: DTYMK were set to Global developmental delay; Intellectual disability; Microcephaly; Seizures; Global brain atrophy; Cardiorespiratory arrest Phenotypes for gene: DTYMK were set to 31271740; 34918187; 35346037 Penetrance for gene: DTYMK were set to Complete Review for gene: DTYMK was set to GREEN Added comment: 4 individuals (from 3 families) harboring biallelic DTYMK pathogenic variants have been reported. Consider inclusion in the current panel with green rating given consistent and relevant phenotype and evidence provided to date [effect of variants (LoF), pathogenesis, similar phenotypes in zebrafish model, etc]. Relevant studies are summarized below. ---- Lam et al (2019 - PMID: 31271740) described two siblings aged 25m and 7y, harboring biallelic DTYMK variants. The phenotype consisted of hypotonia, congenital microcephaly, DD, severe ID. Other shared features included raised serum lactate, pyruvate and alanine. The phenotype was more pronounced in the younger one (epilepticus during febrile illness, epilepsy on multiple anti-convulsants, evidence of regression, etc). Brain MRI revealed marked cerebral atrophy among the findings while a lactate peak was present in spectroscopy. The elder brother developed an episode of sudden onset coma with respiratory failure at the age of 7y. Quartet WES identified compound heterozygosity for a fs and a missense DTYMK variant (NM_012145.3:c.287_320del / p.Asp96Valfs*8 - c.295G>A / p.Ala99Thr). There were no additional findings. Previous genetic panel analysis for epilepsy was unremarkable for the 1st sib. There are two pathways for synthesis of dNTPs, the de novo pathway operating in the cytosol only and the salvage operating in both cytosol and mitochondria. DTYMK encodes (deoxy)thymidylate kinase which catalyzes conversion (phosphorylation) of dTMP to dTDP - a step right after convergence of both pathways - in the dTTP synthesis pathway. Mutations in TK2, an enzyme phosphorylating thymidine in mitochondria to dTMP have been associated with mitochondrial DNA depletion syndrome (MDDS). Given this and as the 2 sibs had raised serum lactate and pyruvate, the authors performed in silico analyses to calculate mtDNA/nDNA ratio dividing the respective read depths for mitochondrial and nuclear DNA obtained from WGS data of the two sibs (blood). This ratio was shown to be reduced in the more severely affected sib (65.5% of control) although this was not the case for the mildly affected brother (114.6%). As a control a non-MDDS mitochondrial cytopathy sample (corresponding to m.8993T>G) was used. The respective ratio which was calculated for a known POLG-related MDDS case was 15.6%. ---- Vanoevelen et al (2022 - PMID: 34918187) describe two unrelated children with hypotonia, absence of developmental progress, microcephaly, seizures (recurrent febrile seizures/myoclonic jerks). Severe cerebral atrophy (with unaffected cerebellum) was observed upon brain imaging. Other findings included puffy body/extremities. Both had complications following respiratory illness leading to demise. CNS pathology in the 1st individual revealed massive neuronal dropout, with sparing of dentate nucleus and brainstem. CMA in both cases was normal. This was also the case for extensive metabolic investigations (which provided no evidence of eventual mitochondrial dysfunction). WES revealed compound heterozygosity for 2 missense variants in the first individual (NM_012145.3:c.382G>A - p.Asp128Asn and c.242C>T - p.Pro81Leu). The second individual, born to consanguineous parents, was homozygous for c.242C>T / p.Pro81Leu. In silico predictions varied although each variant were (mostly) suggestive of a deleterious effect. Variants were both ultrarare without homozygotes in ExAC,. The authors generated a dtymk ko zebrafish model (hmz for a frameshift variant). Zebrafish exhibited markedly smaller eyes and pericardiac edema (3dpf-), twitching movements somewhat reminiscent of epilepsy (at 3dpf), prominent edema of brain and intestine. Head size was significantly smaller at a timepoint prior to brain edema (also after correction for length). Histology provided evidence of empty spaces in brain, suggestive of neurodegeneration, with high amounts of apoptotic cells. dTMPK activity was measured in zebrafish (at 5dpf) as well as in fibroblasts from one individual and in both cases, it was barely detectable and significantly lower compared to wt/htz zebrafish or to the activity in fibroblasts from the parents of the individual tested. In fibroblasts from the same individual with comparison to his parents, the authors demonstrated that DNA replication was impaired (using pulse-EdU staining to quantify cells in S-phase). Assessment of cell proliferation in the brain of dtymk ko zebrafish using phospo-Ser10-Histone H3 (pH3) staining was suggestive of severe proliferation defects in forebrain. Impaired biosynthesis of nucleotides for DNA synthesis/repair would be predicted to result in nucleotide pool imbalance, leading to incorporation of ribonucleotides in genomic DNA with - in turn - impairment of DNA replication and genomic instability (sensitivity to strand breakage). In line with this, genomic DNA of ko zebrafish following alkaline hydrolysis and alkaline gel electrophoresis was shown to migrate at lower position and to be more fragmented indicating increased sensitivity (due to incorporation of ribonucleotides). Visualization of DNA breakage by γH2AX staining, following UV-irradiation of zebrafish embryos revealed persistence of elevated γH2AX levels and DNA damage response signaling, interpreted as increase in unrepaired DNA breaks. mtDNA copy numbers in fibroblasts from the affected individual was somewhat but not significantly lower compared to his parents. Importantly, the copy numbers were similar to controls (N=5) which overall does not support mtDNA depletion as a consequence of DTYMK deficiency. Integrity of mtDNA did not appear to be compromised , with the mitochondrial genome migrating at the expected length of 16,5 kb with no indications of mtDNA deletions for both affected individual and his parents. Activity of the mitochondrial respiratory complexes I-V in fibroblasts from the affected individual was comparable to that of his parents. Overall, there was no evidence for mtDNA depletion (although not studied in muscle biopsy) while functional studies failed to demonstrate mitochondrial dysfunction. The authors discuss other disorders of impaired dTTP metabolism due to mutations in TYMP, RRM2B or CAD. ------ In a recent study using zebrafish model, Hu Frisk et al (2022 - PMID: 35346037) further demonstrate that Dtymk is essential for neurodevelopment providing evidence for expression of a compensatory thymidylate kinase-like enzyme at later stages of development (explaining survival of ko dtymk zebrafish despite the central role of this enzyme in dTTP generation). [Not further reviewed] Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.1540 | SLC5A6 | Arina Puzriakova Phenotypes for gene: SLC5A6 were changed from Feeding difficulties; Failure to thrive; Global developmental delay; Developmental regression; Intellectual disability; Seizures; Microcephaly; Cerebral atrophy; Abnormality of the corpus callosum; Vomiting; Chronic diarrhea; Gastrointestinal hemorrhage; Abnormal immunoglobulin level; Osteopenia; Abnormality of metabolism/homeostasis to Neurodegeneration, infantile-onset, biotin-responsive, OMIM:618973 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.1529 | SLC38A3 |
Konstantinos Varvagiannis gene: SLC38A3 was added gene: SLC38A3 was added to Intellectual disability. Sources: Literature,Other Mode of inheritance for gene: SLC38A3 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: SLC38A3 were set to 34605855 Phenotypes for gene: SLC38A3 were set to Infantile axial hypotonia; Global developmental delay; Intellectual disability; Seizures; Spasticity; Microcephaly; Cerebral atrophy; Cerebellar atrophy; Abnormality of the corpus callosum; Dysphagia; Constipation; Increased serum lactate; Hyperammonemia Penetrance for gene: SLC38A3 were set to Complete Review for gene: SLC38A3 was set to GREEN Added comment: Marafi et al (2021 - PMID: 34605855) describe the phenotype of 10 individuals, belonging to 7 families (6/7 consanguineous), harboring biallelic deleterious SLC38A3 variants. One subject (from fam3) was previously reported in the context of a larger cohort of consanguineous families investigated with exome sequencing (2017, PMID: 31130284). The phenotype overall corresponded to a DEE and features included axial hypotonia (10/10), severe global DD or ID (10/10), seizures (8/10, onset : 1w-15m, NOT observed in 2/10 aged 1y3m and 4y | s. types: tonic-clonic in 3/8, tonic 2/8, focal 2/8 with secondary generalization, myoclonic 1/8, gelastic 1/8 | EEG burst-suppression, hypsarrhythmia in few). Microcephaly was observed in (8/10) and was more commonly postnatal and/or progressive. Variable abnormalities were observed upon brain imaging incl. cerebral (5/10) or cerebellar atrophy (2/10) and abnormal CC (6/10), abnormal myelination for age (6/10). Other phenotypes included visual impairment (9/10), peripheral hypertonia (8/9) constipation (8/9) and dysphagia (7/9), FTT (4/8), movement disorder (3/10). Metabolic studies indicated (transient) elevation of lactate (7/8 - also pyruvate in 2) and elevated plasma ammonia (4/7). Individuals from the 1st family were investigated with ES, and the SLC38A3 splice site variant (NM_006841.6:c.855+1G>T) was the most likely candidate, additional SNVs not contributing to the NDD phenotype. Other affected subjects were ascertained through GeneMatcher/collaborations. In total, 3 different missense and 4 pLoF (1 fs, 2 nonsense, 1 splicing) variants were identified with individuals from 2 families being hmz or cmd htz for missense variants. Variants were absent/ultrarare with no homozygotes in public/in-house databases with several in silico predictions in favor of a deleterious effect. Regions of AOH (around SLC38A3/total) are provided for some individuals/families. Sanger sequencing was used for confirmation and segregation studies (apart from carrier parents in 7/7 fam, 11 unaffected sibs tested in 6/7 fam). The solute carrier (SLC) superfamily of transmembrane transporters - highly expressed in mammalian brain - is involved in exchange of amino-acids (AAs), nutrients, ions, neurotransmitters and metabolites etc across biological membranes with >100 SLC-encoding genes associated with NDDs. SLC38A3 specifically encodes SNAT3, a sodium-coupled neutral amino-acid transporter, principal transporter of Asn, His, Gln (precursor for GABA and glutamate), expressed in brain, liver, kidney, retina and pancreas. In the brain, it localizes to peri-synaptic astrocytes playing an important role in glutamate/GABA-glutamine cycle. While the pLoF variants are predicted to undergo NMD or result in non-functional protein, protein modelling suggested that missense ones affect protein activity or stability. Biochemical and metabolic screening was carried out for several individuals with plasma AAs reported normal (10/10), urinary OAs normal in 9/9, CSF AAs (incl. GABA/glutamine) normal in 2 sibs, CSF lactate normal in 1 indiv. studied. As discussed above plasma ammonia was elevated in 4/7 (2 fam), and 7/10 had elevated lactate and/or pyruvate (2/7). Untargeted metabolomic profiles performed in biofluids (plasma from 3 subjects, CSF:1, urine:1) were suggestive of altered AA and nitrogen metabolism. In particular, alterations in levels of AA known to be transported by SNAT3 were found. 676 molecules overall showed deviation in plasma samples, 630 in urine and 241 in CSF (albeit with no consistent pattern). Perturbations in several biochemical pathways were shown to occur (incl. Gln-,Asn- and His- pathways). Slc38a3-/- mice have reductions in brain glutamate and GABA neurotransmitters in homogenized brain tissue (GABA analytes being normal in plasma samples or the single CSF sample available from affected subjects). Snat3-deficient mice had elevation of plasma urea and normal ammonia levels (urea was low in all human samples and ranged from -2 to -3.5 SD in plasma, ammonia was elevated in 4/7). Slc38a3-/- mice have impaired growth, lethargy and ataxic gait, altered plasma AAs, normal glutamine in plasma with abundance in brain and exhibit early lethality. Plasma AAs were normal in 4 affected individuals, impaired growth observed in 4 and gait impairment was observed in 9/10. Hypoglycemia, previously reported in Slc38a3-/- mice, was not observed in any of the patients although this is presumably explained by diet/feeding intervals with abnormalities in pentose phosphate pathway in one individual hypothesized to be reflective of abn. glucose metabolism. The human phenotypes of microcephaly and seizures were not observed in mice. For mouse studies PMIDs cited by the authors : 27362266, 26490457. There is currently no SLC38A3-related phenotype reported in OMIM. In G2P this gene is incl. in the DD panel (biallelic, confidence: strong, SLC38A3-associated epileptic encephalopathy). SLC38A3 is listed among the primary ID genes in SysID. In PanelApp Australia, SLC38A3 is included with green rating in the epilepsy, ID and microcephaly panels. Consider inclusion with green rating (10 individuals, 7 families, 7 variants, role of SLCs and SLC38A3, alterations in AA/nitrogen metabolism etc) or amber rating (if discordances with mouse model considered). Please consider inclusion in other panels e.g. for microcephaly, CC abnormalities, metabolic disorders, etc. Sources: Literature, Other |
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| Intellectual disability - microarray and sequencing v3.1525 | CACNA2D1 |
Konstantinos Varvagiannis gene: CACNA2D1 was added gene: CACNA2D1 was added to Intellectual disability. Sources: Literature,Other Mode of inheritance for gene: CACNA2D1 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: CACNA2D1 were set to 35293990; 28097321 Phenotypes for gene: CACNA2D1 were set to Abnormal muscle tone; Feeding difficulties; Global developmental delay; Intellectual disability; Seizures; Microcephaly; Abnormality of the corpus callosum; Cerebral atrophy; Abnormality of movement; Cortical visual impairment; Pain insensitivity Penetrance for gene: CACNA2D1 were set to Complete Review for gene: CACNA2D1 was set to GREEN Added comment: Consider inclusion in the current panel with green rating. Recent report of 2 unrelated individuals with DEE due to biallelic CACNA2D1 variants. Both referred to neurology/genetics for hypotonia/severe DD prior to onset of seizures. One further individual with hypotonia and severe ID (seizures not discussed, age unknown). Gene with established role, encoding α2δ-1 subunit of Cav channels. Studies for the variants support loss-of-function as the underlying effect. Eventual contribution of monoallelic variants to NDD-phenotypes discussed (and put in question) in Ref [1] below. There is currently no phenotype for CACNA2D1 in OMIM/G2P. In SysID this gene is listed among the candidates for ID, based on a previous report. CACNA2D1 is not currently included in the ID/epilepsy panels in PanelApp Australia. See also relevant review in epilepsy panel (Dr. H. Lord). Please consider also inclusion in other panels (e.g. microcephaly, corpus callosum, movement disorders, etc). [1] ---- Dahimene et al (2022 - PMID: 35293990) describe the phenotype of 2 unrelated individuals with biallelic CACNA2D1 variants. Overall, the phenotype corresponded to an early-onset DEE, characterized by abnormal muscle tone (axial hypotonia 2/2 with spasticity in extremities in 2/2), feeding difficulties (2/2), profound DD and ID (2/2), microcephaly (2/2 - approx. -2 SD in both), seizures (2/2 - 1st : onset 9m with absences and later generalized seizures, 2nd : onset 11m with hemi-clonic seizures and atypical absences). Other features included cortical visual impairment (2/2) and movement disorder (incl. choreiform movements 2/2, orofacial dyskinesia 2/2 and dystonic episodes 1/2). Brain MRI revealed corpus callosum anomalies (2/2) and cerebral atrophy (2/2). Both had echocardiography (abnormal in 1/2 - tiny PFO) and electrocardiography which was normal. Both exhibited insensibility to pain. Presentation is relevant to the current panel as first symptoms in the first 3 months with severe hypotonia and poor head control (2/2) with evaluation in neurology/genetics preceding onset of seizures in both. Trio ES was performed for both individuals and their (healthy) parents and revealed homozygosity for a fs variant in the first [NM_000722.3:c.818_822dup / p.(Ser275Asnfs*13)] and compound htz for a fs and a missense variant [c.13_23dup / p.(Leu9Alafs*5) and c.626G>A / p.(Gly209Asp)] in the second affected individual, respectively. Eventual additional variants were not discussed. Previous investigations are only provided for the 2nd and were all normal (karyotype, CMA, 15q methylation, epilepsy/neurometabolic gene panels). Voltage-gated calcium channels are heteromultimers comprising different subunits incl. an alpha-1 (α1), α2δ (alpha-2/delta), beta (β) and gamma (γ). CACNA2D1 is one of the 4 genes (CACNA2D1-4) encoding the alpha-2/delta subunit. Its product is post-translationally processed into 2 peptides, an alpha-2 and a delta subunit, held by a disulfide bond. Biallelic variants in CACNA2D2 - also encoding an alpha-2/delta subunit - cause cerebellar atrophy with seizures and variable developmental delay (# 618501). Variant studies support loss-of-function effect for the studied variants, notably by NMD for the fs one, and severe impairment of the Cav2 channel function for the missense one : - CACNA2D1 mRNA was reduced to 6-9% compared with control in fibroblasts from the 1st individual. mRNA levels for the 2nd subject were similar to control. - Quantification of the protein in whole-cell lysates from fibroblasts revealed lower α2δ levels compared to control (10-12% and 31-38% applying to the 1st and 2nd individual). - CACNA2D3 mRNA levels in fibroblasts from the 2nd patient were 2-7x higher compared to the 1st or controls suggesting a possible compensatory effect. CACNA2D2/4 mRNA levels were too low for quantification. - Gly209 lies within the gabapentin and amino-acid binding pocket and this residue is invariable in CACNA2D1/CACNA2D2 in all vertebrates and paralogs. - Transfection of tsA-201 cells with either WT or G209D HA-tagged α2δ revealed reduced cell surface expression for this missense variant (~80, for biotinylated form ~86%). - In tsA-201 cells transfected with HA-tagged Cav2.2/β1b and either α2δ-1-WT, no α2δ-1 or α2δ-1-G209D, WT resulted in increased 13x currents with no increase applying to G209D (or in absence of α2δ). Plasma membrane expression of double (GFP/HA) tagged Cav2.2 was increased upon co-expression with WT α2δ-1 which was not the case for α2δ-1-G209D. - In hippocampal neurons, double (GFP/HA)-tagged Cav2.2 could not be detected at the cell surface in the presence of α2δ-1-G209D (or no α2δ) in contrast with strong expression in presence of α2δ-1-WT. α2δ-1-G209D did not promote trafficking of Cav2.2 into hippocampal neurites, as indicated by reduced signals for both HA and GFP (for cell surface and total Cav2.2 respectively). - Co-expression of double (GFP/HA) tagged Cav2.2 with β1b and either HA-α2δ-1-WT or HA-α2δ-1-G209D in tsA-201 cells, revealed reduced complex formation of G209D with Cav2.2 Co-immunoprecipitated HA-α2δ-1-G209D had higher molecular weight compared to HA-α2δ-1-WT which suggests that α2δ-1-G209D remains as the uncleaved immature form (probably in the ER). Mouse model (several Refs in text): Mild cardiac phenotype and reduced ventricular myocyte Ca current density was observed in hmz ko mice. Similarly to the insensibility to pain human phenotype, mice had delayed neuropathic pain-related responses. Overexpression of a2δ-1 resulted in epileptiform EEG and behavioral arrest, overall supporting a critical role of α2δ-1 for mouse brain. The authors underscore that the parents of both patients (htz carriers) were healthy and review previous literature for association of monoallelic variants with epilepsy, ID and arrhythmogenic disorders (in suppl.) [Refs not here reviewed]. As for the NDD phenotype, CACNA2D1 is within a previously defined small region of overlap for 7q21.11 microdeletions associated with ID+/-epilepsy. The same study did not reveal de novo SNVs in any of the 3 contained genes within this SRO (HGF, CACNA2D1, PCLO) in 4293 patients with NDD [cited PMID: 28240412]. A frameshift variant (c.2625del) was identified in a 13-yo girl with infantile spasms and normal intelligence [cited PMID: 25877686]. A 1-bp insertion (c.659-2_659-1insT / not studied at the mRNA level) was identified in another 14-yo female with ID and epilepsy [cited PMID: 34356170]. The authors state that the phenotype (/differences) of these individuals as well as presence of pLoF CACNA2D1 variants in gnomAD [still pLI of 1] put in question pathogenicity of monoallelic variants for these phenotypes. The role of heterozygous missense variants described in relation to arrhythmogenic disorders is also discussed extensively (some downgraded to LB/VUS, others having a relatively high MAF and presence of 1-2 homozygotes in gnomAD). [2] ---- In an article cited by SysID for CACNA2D1 (2017 - PMID: 28097321), Reuter et al studied with WES and autozygosity mapping individuals with NDD belonging to consanguineous families. As in eTables1/3, a male - single affected individual born to consanguineous parents from Turkey (MR150) - was investigated by singleton ES. This individual was homozygous for a missense CACNA2D1 SNV [NM_000722.2:c.1514C>T;p.(Thr505Ile)]. Prior investigations are unavailable (although individuals with previously known P/LP CNVs were excluded). The phenotype - briefly reported - included hypotonia, severe ID, stereotypic behaviors, inguinal hernia and omphalocele. Presence of seizures was not commented on. The age of this individual was not reported. Sources: Literature, Other |
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| Intellectual disability - microarray and sequencing v3.1518 | NRCAM |
Konstantinos Varvagiannis gene: NRCAM was added gene: NRCAM was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: NRCAM was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: NRCAM were set to 35108495 Phenotypes for gene: NRCAM were set to Hypotonia; Hypertonia; Spasticity; Global developmental delay; Intellectual disability; Microcephaly; Behavioral abnormality; Neuropathy; Hearing abnormality; Abnormality of the eye; Abnormality of the skeletal system; Scoliosis; Abnormality of the face Penetrance for gene: NRCAM were set to Complete Review for gene: NRCAM was set to GREEN Added comment: Kurolap et al (2022 - PMID: 35108495) describe the phenotype of 10 individuals (from 8 families) with biallelic variants in NRCAM. Features included tone abnormalities (hypotonia in 4/10, hypertonia/spasticity in 4/10), DD (8/10 - 7 families) and cognitive impairment (in 7/10 - 6 fam), neuropathy (4/10 - incl. 2 sibs without DD/ID). Other phenotypes incl. FTT (2/8), microcephaly (3/6), variable behavioral issues (3/5), abnormalities from the eyes/vision (6/8 - cataract in 2), abnormal hearing (3/7) or skeletal findings (8/9 - incl. scoliosis in 5). Nonspecific facial features were reported in 5/8. Previous metabolic, genetic (incl. karyotype or CMA, FMR1, testing for Steinert disease or SMA) or other work-up (e.g. muscle biopsy) is reported for several subjects but was normal/non-diagnostic. All were investigated by WES/WGS which revealed biallelic NRCAM variants. Sanger sequencing was used for confirmation and segregation analyses, with compatible results in several affected/unaffected sibs tested. There were no alternative explanations for the NDD phenotype with the exception of one subject with a mosaic functionally characterized LP KRAS variant suspected to contribute to his phenotype. NRCAM encodes neuronal cell adhesion molecule (CAM). CAMs are membrane bound proteins with important role in tissue morphogenesis and maintenance. They mediate interactions between neighboring cells or cells and the extracellular matrix. The L1 subgroup of immunoglobulin CAMS - consisting of L1CAM, neurofascin, NRCAM, CHL1 - is the most abundant in the CNS with several critical functions in CNS development, among others in neural cell differentiation, axonal growth and guidance, myelination, synapse formation. Pathogenic L1CAM (XL) and NFASC variants (AR) are associated with NDD. Different missense (N=7), stopgain/frameshift (N=3), a splice variant (NM_001037132.2:c.2647-2A>G) as well as a deep intronic one (c.230+824G>C / rs575851831). Variants occurred in different domains with a cluster (42%) in the fibronectin III domain. Missense SNVs were ultrarare or not present in gnomAD, occurred in conserved residues, with several in silico predictions in favor of a deleterious effect. Structural modelling suggested that all substitutions occurred at residues exposed to solvent and possible abrogated interaction with other proteins. There were no expression studies performed at the mRNA/protein level. The splice variant is predicted to cause ex22 skipping leading to frameshift. The deep intronic variant is predicted to disrupt a site for spl. regulator SC35 and may cause activation of a cryptic acceptor site with inclusion of a cryptic exon. The zebrafish nrcama gene is the sole ortholog of human NRCAM, with another gene proposed as possible ortholog (nrcamb) mapping upon BLAST analysis to cntn1a. The authors performed CRISPR-Cas9 mutagenesis in zebrafish introducing a partial deletion of ex18 and 19. Mutant zebrafish were viable, displayed altered axonal projections and abnormal swimming behavior (increased movement in darkness). Currently, there is no NRCAM-associated phenotype in OMIM/G2P/SysID. PanelApp Australia includes NRCAM in its ID panel with green rating. Consider inclusion probably with green (>3 individuals/families/variants, segregation, gene in the L1-Ig CAM family causing NDD, zebrafish model) or amber rating (ID not a universal feature, variant effect not studied). Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.1518 | HEATR3 |
Konstantinos Varvagiannis gene: HEATR3 was added gene: HEATR3 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: HEATR3 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: HEATR3 were set to 35213692 Phenotypes for gene: HEATR3 were set to Anemia; Thrombocytopenia; Growth delay; Short stature; Abnormality of the skeletal system; Abnormality of finger; Abnormality of the thumb; Intellectual disability; Obesity; Abnormality of the face Penetrance for gene: HEATR3 were set to Complete Review for gene: HEATR3 was set to AMBER Added comment: O'Donohue et al (2022 - PMID: 35213692) describe the clinical features of 6 individuals (from 4 unrelated families) with biallelic pathogenic HEATR3 variants. These included bone marrow failure (anemia/anemia and thrombocytopenia at presentation), short stature/growth retardation (4/6), facial features (5/6 - in some: straight eyebrows, d-s palpebral fissures, synophrys) and skeletal findings incl. disproportionately short fingers/thumb anomaly. ID was reported in 4/6 individuals from 3 families (all: mild ID | 2/6 without ID). The phenotype corresponded overall to a variant form Diamond-Blackfan anemia (DBA, disorder caused by variants in genes encoding for ribosomal proteins) with additional features. The 1st family (2 affected sibs and parents) underwent WES, not diagnostic for DBA. Analysis suggested variants in HEATR3 (prioritized due to its potential role in ribosome biogenesis) and 4 additional genes as candidates. Collaboration in the European DBA consortium and national DBA consortia led to identification of additional families. HEATR3 encodes Heat-repeat-containing protein 3 or symportin, a protein that co-imports uL5 (encoded by RPL11) and uL18 (RPL5) in the nucleus where they assemble with 5S rRNA to form 5S RNP. The 5S RNP complex incorporates with maturing large ribosomal subunits to form the central protuberance. When 5S RNP is not incorporated, it accumulates and associates with Hdm2 ubiquitin ligase, the later normally targeting p53 proteasomal degradation. The following missense and splice variants were identified (NM_182922): - c.1751G>Α/p.(Gly584Glu) hmz - c.1337G>A/p.(Cys446Tyr) hmz - c.399+1G>T in trans with c.719C>T/p.(Pro240Leu) - c.400T>C/p.(Cys134Arg) hmz Variants were confirmed with Sanger sequencing. They were dispersed across HEATR3 without clustering although they affect residues either in the ARM (38-320) or HEAT (415-675) repeat domains, at positions evolutionary conserved, with in silico predictions in favor of a deleterious effect. With the exception of Cys134Arg (AF:4.11x10-6/no hmz), all were absent from gnomAD. Studies in yeast suggested that deletions in symportin gene (syo1) lead to a mild growth defect and accumulation of 40S subunits. Similarly, two yeast strains engineered to test for the effect of the p.Gly584Glu (yeast p.Gly522Glu/Ala) exhibited growth defect and ribosomal subunit imbalance, both restored by wt Syo1. HA-tagged HEATR3 in HeLa cells suggested that the co-translational capture mechanism to chaperone uL18 (RPL5) is conserved in human cells but was not observed upon expression of the p.Cys446Tyr variant. While HEATR3 transcription was not affected in LCLs from individuals hmz for Gly584Glu or Cys446Tyr, protein levels were barely detectable, suggesting destabilization of the protein. While uL18 accumulates in cytoplasm and nucleus with expected enrichment in nucleolus, upon siRNA knockdown of HEATR3 in HeLa cells this enrichment was lost. Studies in fibroblasts (Gly584Glu) demonstrated reduced uL18 nuclear staining. Overall, HEATR3 was suggested to be important for nuclear import of uL18 (though not for uL5). LCL studies demonstrated pre-rRNA processing defects in patient cells with accumulation of 32S and 12S pre-rRNAs, the former being reminiscent of accumulations observed in individuals with RPL5- and RPL11-related DBA. Expression of wt HEATR3 restored processing defects. LCLs from affected individuals revealed loss of free 60S subunits (as in yeast) with expression of wt cDNA restoring Nl levels. Western blots of LCLs demonstrated that the levels of uL5, uL18 and p53 were not affected (the latter also observed in RPL5-related DBA) Studies of bone marrow smears from 2 affected individuals allowed to conclude in a strong defect in erythroid cell proliferation. Currently, there is no HEATR3-associated phenotype in OMIM, PanelApp Australia, G2P or the SysID database. Consider inclusion in the ID panel with amber (mild ID in >3 individuals/families/variants although not universal feature) or green rating. Also consider inclusion in other possibly relevant panels eg. for cytopenias/congenital anemias, short stature, etc. Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.1485 | MYO5B | Arina Puzriakova Phenotypes for gene: MYO5B were changed from Microvillus inclusion disease, 251850 to Diarrhea 2, with microvillus atrophy, OMIM:251850 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.1478 | FOXR1 |
Zornitza Stark gene: FOXR1 was added gene: FOXR1 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: FOXR1 was set to MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted Publications for gene: FOXR1 were set to 34723967 Phenotypes for gene: FOXR1 were set to Postnatal microcephaly, progressive brain atrophy and global developmental delay Review for gene: FOXR1 was set to AMBER Added comment: 1 patient described with a de novo missense variant. Phenotypes include: postnatal microcephaly, progressive brain atrophy, skeletal abnormalities, brain abnormalities, ophthalmic abnormalities, neuromuscular abnormalities, and dysmorphic features. A variant in ATP1A3 was considered to have contributed to the final phenotype. In vitro functional evidence is supportive of pathogenicity (variant causes protein instability and abnormal nuclear aggregation). A mouse knockout has comparable phenotypes, and a severe survival deficit. Rated amber (1 patient, functional evidence, mouse model). Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.1454 | AR | Arina Puzriakova Phenotypes for gene: AR were changed from Spinal and bulbar muscular atrophy of Kennedy, OMIM:313200 to Androgen insensitivity, OMIM:300068; Androgen insensitivity, partial, with or without breast cancer, OMIM:312300; Hypospadias 1, X-linked, OMIM:300633; Spinal and bulbar muscular atrophy of Kennedy, OMIM:313200 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.1335 | ATP11A |
Zornitza Stark gene: ATP11A was added gene: ATP11A was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: ATP11A was set to MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted Publications for gene: ATP11A were set to 34403372 Phenotypes for gene: ATP11A were set to Neurodevelopmental disorder Review for gene: ATP11A was set to AMBER Added comment: PMID: 34403372: - Single de novo missense variant reported in a patient with developmental delay and neurological deterioration. - Patient MRI showed severe cerebral atrophy, ventriculomegaly, hypomyelination leukodystrophy, thinned corpus callosum. Axonal neuropathy suggested. - K/I heterozygous mice died perinatally. - Functional studies on missense variant show plasma membrane lipid content impairment, reduced ATPase activity etc. gnomAD: some NMD PTCs present, good quality variants found with 4-5 hets. Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.1321 | ARF3 |
Ivone Leong Added comment: Comment on list classification: New gene added by Konstantinos Varvagiannis (Other). This gene is not associated with a phenotype in OMIM or Gene2Phenotype. PMID:34346499, individual 1 also has severe microcephaly (-3.3SD), spasticity, cerebellum atrophy and brainstem atrophy. Individual 2 does not have microcephaly, but has cerebellar hypoplasia. Based on the available evidence, there is currently not enough evidence to support a gene-disease association, therefore this gene has been given an Amber rating. |
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| Intellectual disability - microarray and sequencing v3.1262 | PRICKLE2 | Zornitza Stark reviewed gene: PRICKLE2: Rating: GREEN; Mode of pathogenicity: None; Publications: 34092786; Phenotypes: Neurodevelopmental disorder, global developmental delay, behavioural difficulties ± epilepsy, autistic features, attention deficit hyperactive disorder, psychiatric symptoms; Mode of inheritance: MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.1262 | CHRM1 |
Zornitza Stark gene: CHRM1 was added gene: CHRM1 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: CHRM1 was set to MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted Publications for gene: CHRM1 were set to 34212451; 31981491; 12483218 Phenotypes for gene: CHRM1 were set to Neurodevelopmental delay; intellectual disability; autism Review for gene: CHRM1 was set to AMBER Added comment: PMID: 34212451 - 2 unrelated cases with de novo missense variants (p.Pro380Leu and p.Phe425Ser), one case with early-onset refractory epilepsy, severe disability, and progressive cerebral and cerebellar atrophy, and the second case with mild dysmorphism, global developmental delay, and moderate intellectual disability. In vitro biochemical analyses of p.Pro380Leu demonstrated a reduction in protein levels, impaired cellular trafficking, and defective activation of intracellular signaling pathways. PMID: 31981491 - an autism spectrum disorder (no other information on phenotype, except ascertained to have severe neurodevelopmental delay) case with a de novo missense variant p.(Arg210Leu) PMID: 12483218 - null mouse model assessing memory demonstrated selective cognitive dysfunction. Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.1222 | RNF220 |
Konstantinos Varvagiannis gene: RNF220 was added gene: RNF220 was added to Intellectual disability. Sources: Literature,Other Mode of inheritance for gene: RNF220 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: RNF220 were set to 33964137; 10881263 Phenotypes for gene: RNF220 were set to Leukodystrophy; CNS hypomyelination; Ataxia; Intellectual disability; Sensorineural hearing impairment; Elevated hepatic transaminases; Hepatic fibrosis; Dilated cardiomyopathy; Spastic paraplegia; Dysarthria; Abnormality of the corpus callosum Penetrance for gene: RNF220 were set to Complete Review for gene: RNF220 was set to GREEN Added comment: Sferra et al (2021 - PMID: 33964137) provide extensive evidence that biallelic RNF220 mutations cause a disorder characterized by hypomyelinating leukodystrophy, ataxia (9/9 - onset 1-5y), borderline intellectual functioning (3/9) / intellectual disability (5/9 - in most cases mild), sensorineural deafness (9/9) with complete hearing loss in the first decade of life, hepatopathy (9/9) with associated periportal fibrosis, and dilated cardiomyopathy (9/9) which was fatal. Other neurologic manifestations apart from ataxia incl. hyperreflexia (8/8), spastic paraplegia (9/9), dysarthria (9/9), peripheral neuropathy (4/9), seizures in one case (1/9). Upon brain MRI there was thin corpus callosum (9/9) or cerebellar atrophy in some (2/9). The authors identified homozygosity for 2 recurrent missense RNF220 variants in affected members belonging to these 5 broad consanguineous pedigrees (7 families), namely NM_018150.4:c.1094G>A / p.Arg365Gly in 4 Roma families in the context of a shared haplotype (/founder effect) as well as c.1088G>A / p.Arg363Gly in a large pedigree from southern Italy initially reported by Leuzzi et al (2000 - PMID: 10881263). Extensive segregation analyses were carried out including several affected and unaffected members. RNF220 encodes ring finger protein 220, which functions as an E3 ubiquitin ligase. Previous studies have shown among others a role in modulation of Sonic hedgehog/GLI signaling and cerebellar development Evidence for the role of RNF220 included relevant expression, localization within the cell, interaction partners (lamin B1, 20S proteasome), similarities with other laminopathies in terms of phenotype, etc : *RNF220 has a relevant expression pattern in CNS (based on qRT-PCR analyses in human brain, cerebellum, cerebral cortex / mRNA levels in human fetal CNS with higher expression in cerebellum, spinal cord and cortex / previous GTEx data / protein levels in mouse CNS) *The protein displays nuclear localization based on iPSC cells differentiated to motor neurons (also supported by data from the Human Protein Atlas). Transfection of COS-1 cells demonstrated localization primarily to the nucleus (as also previously demonstrated in HEK293T cells) in vesicle like structures with ASF2/SF2 colocalization suggesting enrichment in nuclear speckles. There was also partial co-distribution with the 20S proteasome. R363Q and R365Q additionally coalesced in the cytoplasm forming protein aggregates/inclusions. *Immunofluorescence studies in patient fibroblasts also confirmed abnormal increase of the protein in the cytoplasm and increased fluorescence with the 20S proteasome. *Proteomic identification of RNF220-interacting proteins in transfected HEK293T cells demonstrated enrichment for all members of the lamin protein family (incl . lamin B1, AC, B2). *RNAi-mediated downregulation of RNF222 in Drosophila suggested altered subcellular localization and accumulation of the fly orthologue for human lamin B1. *Immunoprecipitation of lamin B1 from the nuclear matrix of cerebellar cells suggested significant interaction of endogenous lamin B1 with RNF220, while transfection studies in HEK293T cells for wt/mt suggested reduced binding to endogenous lamin B1 for RNF220 mt compared to wt (more prominent for R365Q). RNF220 mutants also reduced ubiquitination of nuclear lamin B1 compared to wt. *Patient fibroblasts immunostained with different nuclear envelope markers displayed abnormal nuclear shapes with multiple invaginations and lobulations, findings also observed in laminopathies. There is currently no associated phenotype in OMIM or G2P. SysID includes RNF220 among the current primary ID genes. Consider inclusion in panels for leukodystrophies, childhood onset ataxia, sensorineural hearing loss, corpus callosum anomalies, cardiomyopathies, hepatopathies, etc in all cases with green rating. Sources: Literature, Other |
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| Intellectual disability - microarray and sequencing v3.1220 | ARF3 |
Konstantinos Varvagiannis gene: ARF3 was added gene: ARF3 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: ARF3 was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: ARF3 were set to 34346499 Phenotypes for gene: ARF3 were set to Global developmental delay; Intellectual disability; Seizures; Morphological abnormality of the central nervous system Penetrance for gene: ARF3 were set to unknown Review for gene: ARF3 was set to AMBER Added comment: Sakamoto et al (2021 - PMID: 34346499) provide some evidence that monoallelic ARF3 pathogenic variants may be associated with a NDD with brain abnormality. Using trio exome sequencing, the authors identified 2 individuals with NDD harboring de novo ARF3 variants, namely: NM_001659.2:c.200A>T / p.Asp67Val and c.296G>T / p.Arg99Leu. Individual 1 (with Asp67Val / age : 4y10m), appeared to be more severelely affected with prenatal onset progressive microcephaly, severe global DD, epilepsy. Upon MRI there was cerebellar and brainstem atrophy. Individual 2 (Arg99Leu / 14y) had severe DD and ID (IQ of 23), epilepsy and upon MRI cerebellar hypoplasia. This subject did not exhibit microcephaly. Common facial features incl. broad nose, full cheeks, small philtrum, strabismus, thin upper lips and abnormal jaw. There was no evidence of systemic involvement in both. ARF3 encodes ADP-ribosylation factor 3. Adenosine diphosphate ribosylation factors (ARFs) are key proteins for regulation of cargo sorting at the Golgi network, with ARF3 mainly working at the trans-Golgi network. ARFs belong to the small GTP-binding protein (G protein) superfamily. ARF3 switches between an active GTP-bound form and an inactive GDP-bound form, regulated by guanine nucleotide exchange factors (GEFs) and GTPase activating proteins (GAPs) respectively. Members of the ARF superfamily regulate various aspects of membrane traffic, among others in neurons. There are 5 homologs of ARF families, divided in 3 classes. ARF3 and ARF1 belong to class I. Monoallelic ARF1 mutations are associated with Periventricular nodular heterotopia 8 (MIM 618185). In vivo, in vitro and in silico studies for the 2 variants suggest that both impair the Golgi transport system although each variant most likely exerts a different effect (gain-of-function for Arg99Leu vs loss-of-function/dominant-negative for Asp67Val). This was also reflected in somewhat different phenotype of the subjects with the respective variants. Common features included severe DD, epilepsy and brain abnormalities although Asp67Val was associated with diffuse brain atrophy as well as congenital microcephaly and Arg99Leu with cerebellar hypoplasia. Evidence to support the effect of each variant include: Arg99Leu: Had identical Golgi localization to that of wt Had increased binding activity with GGA1, a protein recruited by the GTP-bound active form of ARF3 to the TGN membrane (supporting GoF) In silico structural analysis suggested it may fail to stabilize the conformation of Asp26, resulting in impaired GTP hydrolysis (GoF). In transgenic fruit flies, evaluation of the ARF3 variant toxicity using the rough eye phenotype this variant was associated with increased severity of the r-e phenotype similar to a previously studied GoF variant (Gln71Leu) Asp67Val: Did not show a Golgi-like pattern of localization (similar to Thr31Asn a previously studied dominant-negative variant) Displayed decreased protein stability In silico structural analysis suggested that Asp67Val may lead to compromised binding of GTP or GDP (suggestive of LoF) In transgenic Drosophila eye-specific expression of Asp67Val (similar to Thr31Asn, a known dominant-negative variant) was lethal possibly due to high toxicity in very small amounts in tissues outside the eye. There is no associated phenotype in OMIM, G2P or SysID. Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.1217 | PIDD1 |
Konstantinos Varvagiannis changed review comment from: There is enough evidence to include this gene in the current panel with green rating. Biallelic PIDD1 pathogenic variants have been reported in 26 individuals (11 families) with DD (all), variable degrees of ID (mild to severe), behavioral (eg. aggression/self-mutilation in several, ADHD) and/or psychiatric abnormalities (ASD, psychosis in 5 belonging to 3 families), well-controlled epilepsy is some (9 subjects from 6 families) and MRI abnormalities notably abnormal gyration pattern (pachygyria with predominant anterior gradient) as well as corpus callosum anomalies (commonly thinning) in several. Dysmorphic features have been reported in almost all, although there has been no specific feature suggested. The first reports on the phenotype associated with biallelic PIDD1 mutations were made by Harripaul et al (2018 - PMID: 28397838) and Hu et al (2019 - PMID: 29302074) [both studies investigating large cohorts of individuals with ID from consanguineous families]. Sheikh et al (2021 - PMID: 33414379) provided details on the phenotype of 15 individuals from 5 families including those from the previous 2 reports and studied provided evidence on the role of PIDD1 and the effect of variants. Zaki et al (2021 - PMID: 34163010) reported 11 additional individuals from 6 consanguineous families, summarize the features of all subjects published in the literature and review the neuroradiological features of the disorder. PIDD1 encodes p53-induced death domain protein 1. The protein is part of the PIDDosome, a multiprotein complex also composed of the bipartite linker protein CRADD (also known as RAIDD) and the proform of caspase-2 and induces apoptosis in response to DNA damage. There are 5 potential PIDD1 mRNA transcript variants with NM_145886.4 corresponding to the longest. Similar to the protein encoded by CRADD, PIDD1 contains a death domain (DD - aa 774-893). Constitutive post-translational processing gives PIDD1-N, PIDD1-C the latter further processed into PIDD1-CC (by auto-cleavage). Serine residues at pos. 446 and 588 are involved in this autoprocessing generating PIDD1-C (aa 446-910) and PIDD1-CC (aa 774-893). The latter is needed for caspase-2 activation. Most (if not all) individuals belonged to consanguineous families of different origins and harbored pLoF or missense variants. Variants reported so far include : c.2587C>T; p.Gln863* / c.1909C>T ; p.Arg637* / c.2443C>T / p.Arg815Trp / c.2275-1G>A which upon trap assay was shown to lead to skipping of ex15 with direct splicing form exon14 to the terminal exon 16 (resulting to p.Arg759Glyfs*1 with exlcusion of the entire DD) / c.2584C>T; p.Arg862Trp / c.1340G>A; p.Trp447* / c.2116_2120del; p.Val706His*, c.1564_1565del; p.Gly602fs*26 Evidence so far provided includes: - Biallelic CRADD variants cause a NDD disorder and a highly similar gyration pattern. - Confirmation of splicing effect (eg. for c.2275-1G>A premature stop in position 760) or poor expression (NM_145886.3:c.2587C>T; p.Gln863*). Arg815Trp did not affect autoprocessing or protein stability. - Abnormal localization pattern, loss of interaction with CRADD and failure to activate caspase-2 (MDM2 cleavage assay) [p.Gln863* and Arg815Trp] - Available expression data from GTEx (PIDD1 having broad expression in multiple tissues, but higher in brain cerebellum) as well as BrainSpan and PsychEncode studies suggesting high coexpression of PIDD1, CRADD and CASP2 in many regions in the developing human brain. - Variants in other genes encoding proteins interacting with PIDD1 (MADD, FADD, DNAJ, etc) are associated with NDD. Pidd-1 ko mice (ex3-15 removal) lack however CNS-related phenotypes. These show decreased anxiety but no motor anomalies. This has also been the case with Cradd-/- mice displaying no significant CNS phenotypes without lamination defects. There is currently no associated phenotype in OMIM, PanelApp Australia. PIDD1 is listed in the DD panel of G2P (PIDD1-relared NDD / biallelic / loss of function / probable) . SysID includes PIDD1 among the current primary ID genes. Overall the gene appears to be relevant for the epilepsy panel, panels for gyration and/or corpus callosum anomalies etc. Sources: Literature, Other; to: There is enough evidence to include this gene in the current panel with green rating. Biallelic PIDD1 pathogenic variants have been reported in 26 individuals (11 families) with DD (all), variable degrees of ID (mild to severe), behavioral (eg. aggression/self-mutilation in several, ADHD) and/or psychiatric abnormalities (ASD, psychosis in 5 belonging to 3 families), well-controlled epilepsy is some (9 subjects from 6 families) and MRI abnormalities notably abnormal gyration pattern (pachygyria with predominant anterior gradient) as well as corpus callosum anomalies (commonly thinning) in several. Dysmorphic features have been reported in almost all, although there has been no specific feature suggested. The first reports on the phenotype associated with biallelic PIDD1 mutations were made by Harripaul et al (2018 - PMID: 28397838) and Hu et al (2019 - PMID: 29302074) [both studies investigating large cohorts of individuals with ID from consanguineous families]. Sheikh et al (2021 - PMID: 33414379) provided details on the phenotype of 15 individuals from 5 families including those from the previous 2 reports and studied provided evidence on the role of PIDD1 and the effect of variants. Zaki et al (2021 - PMID: 34163010) reported 11 additional individuals from 6 consanguineous families, summarize the features of all subjects published in the literature and review the neuroradiological features of the disorder. PIDD1 encodes p53-induced death domain protein 1. The protein is part of the PIDDosome, a multiprotein complex also composed of the bipartite linker protein CRADD (also known as RAIDD) and the proform of caspase-2 and induces apoptosis in response to DNA damage. There are 5 potential PIDD1 mRNA transcript variants with NM_145886.4 corresponding to the longest. Similar to the protein encoded by CRADD, PIDD1 contains a death domain (DD - aa 774-893). Constitutive post-translational processing gives PIDD1-N, PIDD1-C the latter further processed into PIDD1-CC (by auto-cleavage). Serine residues at pos. 446 and 588 are involved in this autoprocessing generating PIDD1-C (aa 446-910) and PIDD1-CC (aa 774-893). The latter is needed for caspase-2 activation. Most (if not all) individuals belonged to consanguineous families of different origins and harbored pLoF or missense variants. Variants reported so far include : c.2587C>T; p.Gln863* / c.1909C>T ; p.Arg637* / c.2443C>T / p.Arg815Trp / c.2275-1G>A which upon trap assay was shown to lead to skipping of ex15 with direct splicing form exon14 to the terminal exon 16 (resulting to p.Arg759Glyfs*1 with exlcusion of the entire DD) / c.2584C>T; p.Arg862Trp / c.1340G>A; p.Trp447* / c.2116_2120del; p.Val706His*, c.1564_1565del; p.Gly602fs*26 Evidence so far provided includes: - Biallelic CRADD variants cause a NDD disorder and a highly similar gyration pattern. - Confirmation of splicing effect (eg. for c.2275-1G>A premature stop in position 760) or poor expression (NM_145886.3:c.2587C>T; p.Gln863*). Arg815Trp did not affect autoprocessing or protein stability. - Abnormal localization pattern, loss of interaction with CRADD and failure to activate caspase-2 (MDM2 cleavage assay) [p.Gln863* and Arg815Trp] - Available expression data from GTEx (PIDD1 having broad expression in multiple tissues, but higher in brain cerebellum) as well as BrainSpan and PsychEncode studies suggesting high coexpression of PIDD1, CRADD and CASP2 in many regions in the developing human brain. - Variants in other genes encoding proteins interacting with PIDD1 (MADD, FADD, DNAJ, etc) are associated with NDD. Pidd-1 ko mice (ex3-15 removal) lack however CNS-related phenotypes. These show decreased anxiety but no motor anomalies. This has also been the case with Cradd-/- mice displaying no significant CNS phenotypes without lamination defects. There is currently no associated phenotype in OMIM, PanelApp Australia. PIDD1 is listed in the DD panel of G2P (PIDD1-related NDD / biallelic / loss of function / probable) . SysID includes PIDD1 among the current primary ID genes. Overall the gene appears to be relevant for the epilepsy panel, panels for gyration and/or corpus callosum anomalies etc. Sources: Literature, Other |
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| Intellectual disability - microarray and sequencing v3.1217 | PIDD1 |
Konstantinos Varvagiannis gene: PIDD1 was added gene: PIDD1 was added to Intellectual disability. Sources: Literature,Other Mode of inheritance for gene: PIDD1 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: PIDD1 were set to 28397838; 29302074; 33414379; 34163010 Phenotypes for gene: PIDD1 were set to Global developmental delay; Intellectual disability; Seizures; Autism; Behavioral abnormality; Psychosis; Pachygyria; Lissencephaly; Abnormality of the corpus callosum Penetrance for gene: PIDD1 were set to Complete Review for gene: PIDD1 was set to GREEN Added comment: There is enough evidence to include this gene in the current panel with green rating. Biallelic PIDD1 pathogenic variants have been reported in 26 individuals (11 families) with DD (all), variable degrees of ID (mild to severe), behavioral (eg. aggression/self-mutilation in several, ADHD) and/or psychiatric abnormalities (ASD, psychosis in 5 belonging to 3 families), well-controlled epilepsy is some (9 subjects from 6 families) and MRI abnormalities notably abnormal gyration pattern (pachygyria with predominant anterior gradient) as well as corpus callosum anomalies (commonly thinning) in several. Dysmorphic features have been reported in almost all, although there has been no specific feature suggested. The first reports on the phenotype associated with biallelic PIDD1 mutations were made by Harripaul et al (2018 - PMID: 28397838) and Hu et al (2019 - PMID: 29302074) [both studies investigating large cohorts of individuals with ID from consanguineous families]. Sheikh et al (2021 - PMID: 33414379) provided details on the phenotype of 15 individuals from 5 families including those from the previous 2 reports and studied provided evidence on the role of PIDD1 and the effect of variants. Zaki et al (2021 - PMID: 34163010) reported 11 additional individuals from 6 consanguineous families, summarize the features of all subjects published in the literature and review the neuroradiological features of the disorder. PIDD1 encodes p53-induced death domain protein 1. The protein is part of the PIDDosome, a multiprotein complex also composed of the bipartite linker protein CRADD (also known as RAIDD) and the proform of caspase-2 and induces apoptosis in response to DNA damage. There are 5 potential PIDD1 mRNA transcript variants with NM_145886.4 corresponding to the longest. Similar to the protein encoded by CRADD, PIDD1 contains a death domain (DD - aa 774-893). Constitutive post-translational processing gives PIDD1-N, PIDD1-C the latter further processed into PIDD1-CC (by auto-cleavage). Serine residues at pos. 446 and 588 are involved in this autoprocessing generating PIDD1-C (aa 446-910) and PIDD1-CC (aa 774-893). The latter is needed for caspase-2 activation. Most (if not all) individuals belonged to consanguineous families of different origins and harbored pLoF or missense variants. Variants reported so far include : c.2587C>T; p.Gln863* / c.1909C>T ; p.Arg637* / c.2443C>T / p.Arg815Trp / c.2275-1G>A which upon trap assay was shown to lead to skipping of ex15 with direct splicing form exon14 to the terminal exon 16 (resulting to p.Arg759Glyfs*1 with exlcusion of the entire DD) / c.2584C>T; p.Arg862Trp / c.1340G>A; p.Trp447* / c.2116_2120del; p.Val706His*, c.1564_1565del; p.Gly602fs*26 Evidence so far provided includes: - Biallelic CRADD variants cause a NDD disorder and a highly similar gyration pattern. - Confirmation of splicing effect (eg. for c.2275-1G>A premature stop in position 760) or poor expression (NM_145886.3:c.2587C>T; p.Gln863*). Arg815Trp did not affect autoprocessing or protein stability. - Abnormal localization pattern, loss of interaction with CRADD and failure to activate caspase-2 (MDM2 cleavage assay) [p.Gln863* and Arg815Trp] - Available expression data from GTEx (PIDD1 having broad expression in multiple tissues, but higher in brain cerebellum) as well as BrainSpan and PsychEncode studies suggesting high coexpression of PIDD1, CRADD and CASP2 in many regions in the developing human brain. - Variants in other genes encoding proteins interacting with PIDD1 (MADD, FADD, DNAJ, etc) are associated with NDD. Pidd-1 ko mice (ex3-15 removal) lack however CNS-related phenotypes. These show decreased anxiety but no motor anomalies. This has also been the case with Cradd-/- mice displaying no significant CNS phenotypes without lamination defects. There is currently no associated phenotype in OMIM, PanelApp Australia. PIDD1 is listed in the DD panel of G2P (PIDD1-relared NDD / biallelic / loss of function / probable) . SysID includes PIDD1 among the current primary ID genes. Overall the gene appears to be relevant for the epilepsy panel, panels for gyration and/or corpus callosum anomalies etc. Sources: Literature, Other |
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| Intellectual disability - microarray and sequencing v3.1201 | CAMK4 |
Konstantinos Varvagiannis gene: CAMK4 was added gene: CAMK4 was added to Intellectual disability. Sources: Literature,Other Mode of inheritance for gene: CAMK4 was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: CAMK4 were set to 30262571; 33098801; 33211350 Phenotypes for gene: CAMK4 were set to Global developmental delay; Intellectual disability; Autism; Behavioral abnormality; Abnormality of movement; Dystonia; Ataxia; Chorea; Myoclonus Penetrance for gene: CAMK4 were set to Complete Review for gene: CAMK4 was set to GREEN Added comment: 3 publications by Zech et al (2018, 2020 - PMIDs : 30262571, 33098801, 33211350) provide clinical details on 3 individuals, each harboring a private de novo CAMK4 variant. Overlapping features included DD, ID, behavoral issues, autism and abnormal hyperkinetic movements. Dystonia and chorea in all 3 appeared 3-20 years after initial symptoms. CAMK4 encodes Calcium/Calmodulin-dependent protein kinase IV, an important mediator of calcium-mediated activity and dynamics, particularly in the brain. It is involved in neuronal transmission, synaptic plasticity, and neuronal gene expression required for brain development and neuronal homeostasis (summary by OMIM based on Zech et al, 2018). The 473 aa enzyme has a protein kinase domain (aa 46-300) and a C-terminal autoregulatory domain (aa 305-341) the latter comprising an autoinhibitory domain (AID / aa 305-321) and a calmodulin-binding domain (CBD / aa 322-341) [NP_001735.1 / NM_001744.4 - also used below]. Variants in all 3 subjects were identified following trio-WES and were in all cases protein-truncating, mapping to exon 10 or exon 10-intron 10 junction, expected to escape NMD and cause selective abrogation of the autoinhibitory domain (aa 305-321) leading overall to gain-of-function. Variation databases include pLoF CAMK4 variants albeit in all cases usptream or downstream of this region (pLI of this gene in gnomAD: 0.51). Variants leading to selective abrogation of the autoregulatory domain have not been reported. Extensive evidence for the GoF effect of the variant has been provided in the first publication. Several previous studies have demonstrated that abrogation of the AID domain leads to consitutive activation (details below). Mouse models - though corresponding to homozygous loss of function - support a role for CAMKIV in cognitive and motor symptoms. Null mice display tremulous and ataxic movements, deficiencies in balance and sensorimotor performance associated with reduced number of Purkinje neurons (Ribar et al 2000, PMID: 11069976 - not reviewed). Wei et al (2002, PMID: 12006982 - not reviewed) provided evidence for alteration in hippocampal physiology and memory function. Heterozygous mutations in other genes for calcium/calmodulin-dependent protein kinases (CAMKs) e.g. CAMK2A/CAMK2B (encoding subunits of CAMKII) have been reported in individuals with ID. --- The proband in the first publication (PMID: 30262571) was a male with DD, ID, behavioral difficulties (ASD, autoaggression, stereotypies) and hyperkinetic movement disorder (myoclonus, chorea, ataxia) with severe generalized dystonia (onset at the age of 13y). Brain MRI demonstrated cerebellar atrophy. Extensive work-up incl. karyotyping, CMA, DYT-TOR1A, THAP1, GCH1, SCA1/2/3/6/7/8/12/17, Friedreich's ataxia and FMR1 analysis was negative.F Trio WES identified a dn splice site variant (c.981+1G>A) in the last exon-intron junction. RT-PCR followed by gel electrophoresis and Sanger in fibroblasts from an affected and control subject revealed that the proband had - as predicted by the type/location of the variant - in equal amount 2 cDNA products, a normal as well as a truncated one. Sequencing of the shortest revealed utilization of a cryptic donor splice site upstream of the mutated donor leading to a 77bp out-of-frame deletion and introduction of a premature stop codon in the last codon (p.Lys303Serfs*28). Western blot in fibroblast cell lines revealed 2 bands corresponding to the normal protein product as well as to the p.Lys303Serfs*28 although expression of the latter was lower than that of the full length protein. Several previous studies have shown that mutant CAMKIV species that lack the autoinhibitory domain are consitutively active (several Refs provided). Among others Chatila et al (1996, PMID: 8702940) studied an in vitro-engineered truncation mutant (Δ1-317 - truncation at position 317 of the protein) with functionally validated gain-of-function effect. To prove enhanced activity of the splicing variant, Zech et al assessed phosphorylation of CREB (cyclic AMP-responsive element binding protein), a downstream substrate of CAMKIV. Immunobloting revealed significant increase of CREB phosphorylation in patient fibroblasts compared to controls. Overactivation of CAMKIV signaling was reversed when cells were treated with STO-609 an inhibitor of CAMKK, the ustream activator of CAMKIV. Overall the authors demonstrated that loss of CAMKIV autoregulatory domain due to this splice variant had a gain-of-function effect. ---- Following trio-WES, Zech et al (2020 - PMID: 33098801) identified another relevant subject within cohort of 764 individuals with dystonia. This 12-y.o. male, harboring a different variant affecting the same donor site (c.981+1G>T), presented DD, ID, dystonia (onset at 3y) and additional movement disorders (myoclonus, ataxia) as well as similar behavior (ASD, autoaggression, stereotypies). [Details in suppl. p20]. ---- Finally Zech et al (2020 - PMID: 33211350) reported on a 24-y.o. woman with adolescence onset choreodystonia. Other features included DD, moderate ID, absence seizures in infancy, OCD with anxiety and later diagnosis of ASD. Trio WES revealed a dn stopgain variant (c.940C>T; p.Gln314*). ---- There is no associated phenotype in OMIM, G2P, PanelApp AUS. In SysID CAMK4 is listed among the current primary ID genes. ---- Please consider inclusion in other relevant panels. Sources: Literature, Other |
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| Intellectual disability - microarray and sequencing v3.1188 | HEATR5B | Ivone Leong Classified gene: HEATR5B as Amber List (moderate evidence) | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.1188 | HEATR5B | Ivone Leong Gene: heatr5b has been classified as Amber List (Moderate Evidence). | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.1187 | HEATR5B | Ivone Leong Tag watchlist tag was added to gene: HEATR5B. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.1187 | HEATR5B | Ivone Leong Phenotypes for gene: HEATR5B were changed from pontocerebellar hypoplasia; intellectual disability; seizures to pontocerebellar hypoplasia, MONDO:0020135; intellectual disability, MONDO:0001071; seizures | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.1167 | HID1 |
Zornitza Stark gene: HID1 was added gene: HID1 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: HID1 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: HID1 were set to 33999436 Phenotypes for gene: HID1 were set to Syndromic infantile encephalopathy; Hypopituitarism Review for gene: HID1 was set to GREEN Added comment: 7 individuals from 6 unrelated families reported. Clinical features included: hypopituitarism in combination with brain atrophy, thin corpus callosum, severe developmental delay, visual impairment, and epilepsy. Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.1167 | HEATR5B |
Zornitza Stark gene: HEATR5B was added gene: HEATR5B was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: HEATR5B was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: HEATR5B were set to 33824466 Phenotypes for gene: HEATR5B were set to pontocerebellar hypoplasia; intellectual disability; seizures Review for gene: HEATR5B was set to AMBER Added comment: Four affected children from two families presenting with pontocerebellar hypoplasiawith neonatal seizures, severe ID and motor delay. Two homozygous splice variants were reported (c.5051–1G>A and c.5050+4A>G) in intron 31 of HEATR5B gene. Aberrant splicing was found in patient fibroblasts, which correlated with reduced levels of HEATR5B protein. Homozygous knockout mice were not viable Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.1152 | AR | Arina Puzriakova Phenotypes for gene: AR were changed from SPINAL AND BULBAR MUSCULAR ATROPHY to Spinal and bulbar muscular atrophy of Kennedy, OMIM:313200 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.1149 | UFSP2 | Sarah Leigh changed review comment from: The founder variant rs142500730 appears to the be causal for pediatric neurodevelopmental anomalies and epilepsy feautres in over seven Asian families form different locations.; to: The Q2_21_expert_review tag has been added to consider the evidence for the founder variant rs142500730, which appears to the be causal for pediatric neurodevelopmental anomalies and epilepsy feautres in over seven Asian families form different locations. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.1145 | GEMIN5 |
Arina Puzriakova Added comment: Comment on list classification: New gene added by Zornitza Stark (Australian Genomics). There is sufficient evidence to promote this gene to Green at the next GMS panel update (see details below). ----- Kour et al. 2021 (PMID: 33963192) report 30 individuals from 22 unrelated families with biallelic variants in the GEMIN5 gene. All affected individuals displayed predominantly motor DD, although cognitive and speech delays were also seen in most patients (18/19). 23/30 had central hypotonia, and variable appendicular spasticity was observed in 13/30 cases. 8 individuals were nonambulatory, while all ambulatory patients (19) had a gait ataxia. Brain MRI in all cases showed cerebellar atrophy. Variants perturbed the subcellular distribution, stability, and expression of GEMIN5 protein and its interacting partners, and disrupted snRNP complex assembly formation in patient iPSC-derived neurons, suggesting a LoF mechanism. Knockdown in Drosophila lead to developmental defects, motor dysfunction, and a reduced lifespan GEMIN5 is associated with a relevant phenotype in OMIM (Neurodevelopmental disorder with cerebellar atrophy and motor dysfunction, MIM# 619333) but is not yet listed in G2P. |
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| Intellectual disability - microarray and sequencing v3.1144 | GEMIN5 | Arina Puzriakova Phenotypes for gene: GEMIN5 were changed from Neurodevelopmental disorder with cerebellar atrophy and motor dysfunction, MIM# 619333 to Neurodevelopmental disorder with cerebellar atrophy and motor dysfunction, OMIM:619333 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.1120 | GEMIN5 |
Zornitza Stark gene: GEMIN5 was added gene: GEMIN5 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: GEMIN5 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: GEMIN5 were set to 33963192 Phenotypes for gene: GEMIN5 were set to Neurodevelopmental disorder with cerebellar atrophy and motor dysfunction, MIM# 619333 Review for gene: GEMIN5 was set to GREEN gene: GEMIN5 was marked as current diagnostic Added comment: Neurodevelopmental disorder with cerebellar atrophy and motor dysfunction (NEDCAM) is an autosomal recessive disorder characterized by global developmental delay with prominent motor abnormalities, mainly axial hypotonia, gait ataxia, and appendicular spasticity. Affected individuals have cognitive impairment and speech delay; brain imaging shows cerebellar atrophy. 30 individuals from 22 unrelated families reported. Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.1094 | UFSP2 | Sarah Leigh edited their review of gene: UFSP2: Added comment: The founder variant rs142500730 appears to the be causal for pediatric neurodevelopmental anomalies and epilepsy feautres in over seven Asian families form different locations.; Changed rating: GREEN | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.1093 | UFSP2 | Sarah Leigh Added comment: Comment on phenotypes: No OMIM reference for the pediatric neurodevelopmental anomalies and epilepsy feautres. Monoallelic variants have previously been associated with skeletal dysplasias (PMIDs 28892125;26428751;32755715), but there does not appear to be any phenotypic overlap between these and the phenotype seen for the biallelic rs142500730. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.1078 | TRAPPC6B | Arina Puzriakova Phenotypes for gene: TRAPPC6B were changed from Neurodevelopmental disorder with microcephaly, epilepsy, and brain atrophy, 617862 to Neurodevelopmental disorder with microcephaly, epilepsy, and brain atrophy, OMIM:617862 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.1066 | UBTF | Arina Puzriakova Phenotypes for gene: UBTF were changed from developmental regression; motor and language regression; developmental delay; Neurodegeneration, childhood-onset, with brain atrophy, 617672 to Neurodegeneration, childhood-onset, with brain atrophy, OMIM:617672 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.1034 | NEUROD2 |
Arina Puzriakova gene: NEUROD2 was added gene: NEUROD2 was added to Intellectual disability. Sources: Literature Q2_21_rating tags were added to gene: NEUROD2. Mode of inheritance for gene: NEUROD2 was set to MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted Publications for gene: NEUROD2 were set to 16504944; 30323019; 33438828 Phenotypes for gene: NEUROD2 were set to Developmental and epileptic encephalopathy 72, OMIM:618374 Review for gene: NEUROD2 was set to GREEN Added comment: NEUROD2 is associated with a relevant phenotype in OMIM (MIM# 618374), but is not yet listed in Gene2Phenotype. - PMID: 30323019 (2019) - Two unrelated children with refractory early-infantile epileptic encephalopathy. Developmental delay (DD) preceded onset of seizures in both cases, with signs of DD becoming evident at 2-4 months and seizures arising at 5 months of age. Patient 1 became seizure-free after introducing a ketogenic diet at 16 months; however, an EEG at 22 months remained abnormal and she continues to have severe GDD with no independent sitting, walking or speaking at the chronological age of 3 years and 2 months. Patient 2 became seizure-free when a vagal nerve stimulator (VNS) was placed at 16 months of age. He displayed significant improvement on EEG and subsequently began regaining neurodevelopmental milestones. WES revealed different de novo variants in the NEUROD2 gene (P1: c.388G>C, p.E130Q; P2: c.401T>C, p.M134T, respectively). Knockdown of the neurod2 in Xenopus tropicalis tadpoles resulted in abnormal swimming behaviour and progressive seizures followed by periods of immobility. Overexpression of wild-type human NEUROD2 in tadpoles induced non-neuronal cells to differentiate into neurons - on the other hand, overexpression of the mutant alleles failed to to cause any (p.E130Q) or a comparable degree (p.M134T) of ectopic neuronal induction as seen with the wild-type protein. - Conference poster (Genomics of Rare Disease 2021) - 'Neuronal Differentiation Factor 2 (NEUROD2) Pathogenic Variant as a Molecular Aetiology of Infantile Spasm ' by Sakpichaisakul et al, QSNICH, Thailand - In a 15 month-old female with infantile spasm, trio exome sequencing revealed a de novo variant in NEUROD2 (c.388G>C, p.E130Q). She was born of non-consanguineous healthy parents with no family history of epilepsy. Poor eye contact and no social smile were noted in the first few months, followed by the first infantile spasm at 5 months of age. This was initially controlled by combined vigabatrin and prednisolone therapy - however relapsing seizures were detected at 15 months. Sequential treatment with vigabatrin following prednisolone resulted in cessation of seizures, and subsequently regaining of neurodevelopmental milestones (sitting without support, grabbing objects without pincer grasp and speaking one single word) ----- Cases without seizures - - PMID: 33438828 (2021) - Adolescent (14 yrs old) with GDD but without seizures who was found to have a novel de novo NEUROD2 missense variant (c.488 T > C, p.L163P). An additional individual (12 yrs) with DD and a different missense NEUROD2 (c.703G>A, p.A235T) was also identified, but lacking parental samples for segregation analysis. Functional analysis in Xenopus laevis revealed that injection of the p.L163P mRNA variant resulted in a defective ability to induce ectopic neurons in tadpoles as compared with wild-type NEUROD2 mRNA, while the p.A235T variant functioned similarly to wild-type. Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.1018 | MAPKAPK5 |
Zornitza Stark gene: MAPKAPK5 was added gene: MAPKAPK5 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: MAPKAPK5 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: MAPKAPK5 were set to 3344202 Phenotypes for gene: MAPKAPK5 were set to Developmental delay, variable brain anomalies, congenital heart defects, dysmorphism Review for gene: MAPKAPK5 was set to GREEN gene: MAPKAPK5 was marked as current diagnostic Added comment: 3 individuals from 2 families with severe developmental delay, variable brain anomalies, congenital heart defects, dysmorphic facial features, and a distinctive type of synpolydactyly with an additional hypoplastic digit between the fourth and fifth digits of hands and/or feet. Exome sequencing identified different homozygous truncating variants in MAPKAPK5 in both families, segregating with disease and unaffected parents as carriers. Patient-derived cells showed no expression of MAPKAPK5 protein isoforms and reduced levels of the MAPKAPK5-interacting protein ERK3. F-actin recovery after latrunculin B treatment was found to be less efficient in patient-derived fibroblasts than in control cells, supporting a role of MAPKAPK5 in F-actin polymerization. Borderline Amber/Green but high impact variants and a distinctive phenotype with some functional data. Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.1018 | FAR1 | Zornitza Stark edited their review of gene: FAR1: Added comment: PMID 33239752: 12 patients with paediatric onset spastic paraparesis and bilateral congenital/juvenile cataracts. Most also had speech and gross motor developmental delay and truncal hypotonia. Exome sequencing identified de novo variants affecting the Arg480 residue in FAR1 (p.Arg480Cys/His/Leu). Further functional studies in fibroblasts showed that these variants cause a disruption of the plasmalogen-dependent feedback regulation of FAR1 protein levels leading to uncontrolled ether lipid production.; Changed rating: GREEN; Changed publications: 25439727, 33239752; Changed phenotypes: Peroxisomal fatty acyl-CoA reductase 1 disorder, MIM#616154, spastic paraparesis and bilateral cataracts; Changed mode of inheritance: BOTH monoallelic and biallelic, autosomal or pseudoautosomal | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.981 | PIGU | Arina Puzriakova Phenotypes for gene: PIGU were changed from Glycosylphosphatidylinositol biosynthesis defect 2, 618590; Global developmental delay; Intellectual disability; Seizures; Cerebral atrophy; Cerebellar hypoplasia; Scoliosis to Neurodevelopmental disorder with brain anomalies, seizures, and scoliosis, OMIM:618590 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.767 | HPDL | Arina Puzriakova Phenotypes for gene: HPDL were changed from spastic paraplegia; spastic tetraplegia; microcephaly; brain atrophy; epilepsy; severe intellectual; motor disability to Neurodevelopmental disorder with progressive spasticity and brain white matter abnormalities, OMIM:619026; Neurodevelopmental disorder with progressive spasticity and brain white matter abnormalities, MONDO:0033613 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.760 | HPDL |
Evan Reid gene: HPDL was added gene: HPDL was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: HPDL was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: HPDL were set to PMID: 32707086; 33188300 Phenotypes for gene: HPDL were set to spastic paraplegia; spastic tetraplegia; microcephaly; brain atrophy; epilepsy; severe intellectual; motor disability Penetrance for gene: HPDL were set to Complete Review for gene: HPDL was set to GREEN Added comment: Newly identified gene that can give a phenotype ranging from infantile epileptic encephalopathy with severe developmental delay/intellectual disability to juvenile onset progressive spastic paraplegia. Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.750 | PIGK | Sarah Leigh Phenotypes for gene: PIGK were changed from Neurodevelopmental disorder with hypotonia and cerebellar atrophy, with or without seizures 618879 to Neurodevelopmental disorder with hypotonia and cerebellar atrophy, with or without seizures OMIM:618879 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.729 | TANC2 | Arina Puzriakova reviewed gene: TANC2: Rating: GREEN; Mode of pathogenicity: None; Publications: 31616000, 33160097, 30021165; Phenotypes: TANC2-related neurodevelopmental and psychiatric disorder, OMIM:618906; Mode of inheritance: MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.716 | TRAPPC12 | Arina Puzriakova Phenotypes for gene: TRAPPC12 were changed from Encephalopathy, progressive, early-onset, with brain atrophy and spasticity, 617669; Developmental delay to Encephalopathy, progressive, early-onset, with brain atrophy and spasticity, OMIM:617669; Early-onset progressive encephalopathy-hearing loss-pons hypoplasia-brain atrophy syndrome, MONDO:0044696 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.714 | TRAPPC12 | Arina Puzriakova reviewed gene: TRAPPC12: Rating: GREEN; Mode of pathogenicity: None; Publications: 32369837; Phenotypes: Encephalopathy, progressive, early-onset, with brain atrophy and spasticity, OMIM:617669, Early-onset progressive encephalopathy-hearing loss-pons hypoplasia-brain atrophy syndrome, MONDO:0044696; Mode of inheritance: BIALLELIC, autosomal or pseudoautosomal | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.709 | GLS_GCA |
Arina Puzriakova STR: GLS_GCA was added STR: GLS_GCA was added to Intellectual disability. Sources: Literature Mode of inheritance for STR: GLS_GCA was set to BIALLELIC, autosomal or pseudoautosomal Publications for STR: GLS_GCA were set to 30970188 Phenotypes for STR: GLS_GCA were set to Global developmental delay, progressive ataxia, and elevated glutamine, OMIM:618412; Global developmental delay, progressive ataxia, and elevated glutamine, MONDO:0032733 Review for STR: GLS_GCA was set to GREEN Added comment: - PMID: 30970188 (2019) - Three unrelated cases who presented with an early-onset global developmental delay, progressive ataxia, and elevated levels of glutamine. One patient also showed cerebellar atrophy. All 3 individuals harboured a large trinucleotide (GCA) repeat expansion in the 5' UTR (length: 680-1,500-copy repeats). The repeat expansion was found in homozygosity in 1 case, and occurred in compound heterozygosity with an SNV in the other two cases (missense and frameshift variant, respectively). Functional analysis showed the repeat expansion results in reduced expression and glutaminase deficiency. Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.692 | TBCD | Arina Puzriakova Phenotypes for gene: TBCD were changed from Encephalopathy, progressive, early-onset, with brain atrophy and thin corpus callosum 617193 to Encephalopathy, progressive, early-onset, with brain atrophy and thin corpus callosum, OMIM:617193; Early-onset progressive diffuse brain atrophy-microcephaly-muscle weakness-optic atrophy syndrome, MONDO:0044646 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.681 | KCNMA1 | Arina Puzriakova Phenotypes for gene: KCNMA1 were changed from Cerebellar atrophy, developmental delay, and seizures, 617643; Paroxysmal nonkinesigenic dyskinesia, 3, with or without generalized epilepsy, 609446 to Cerebellar atrophy, developmental delay, and seizures, OMIM:617643; Cerebellar atrophy, developmental delay, and seizures, MONDO:0060551; Paroxysmal nonkinesigenic dyskinesia, 3, with or without generalized epilepsy, OMIM:609446; Generalized epilepsy-paroxysmal dyskinesia syndrome, MONDO:0012276; Liang-Wang syndrome, OMIM:618729; Liang-Wang syndrome, MONDO:0032886; {Epilepsy, idiopathic generalized, susceptibility to, 16}, OMIM:618596; Epilepsy, idiopathic generalized, susceptibility to, 16, MONDO:0032827 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.678 | KCNMA1 | Arina Puzriakova reviewed gene: KCNMA1: Rating: GREEN; Mode of pathogenicity: None; Publications: 26195193, 27567911, 29330545, 29545233, 31152168, 31427379; Phenotypes: Cerebellar atrophy, developmental delay, and seizures, OMIM:617643, Cerebellar atrophy, developmental delay, and seizures, MONDO:0060551, Paroxysmal nonkinesigenic dyskinesia, 3, with or without generalized epilepsy, OMIM:609446, Generalized epilepsy-paroxysmal dyskinesia syndrome, MONDO:0012276, Liang-Wang syndrome, OMIM:618729, Liang-Wang syndrome, MONDO:0032886, {Epilepsy, idiopathic generalized, susceptibility to, 16}, OMIM:618596, Epilepsy, idiopathic generalized, susceptibility to, 16, MONDO:0032827; Mode of inheritance: BOTH monoallelic and biallelic, autosomal or pseudoautosomal | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.677 | H3F3B |
Arina Puzriakova changed review comment from: Currently not associated with any phenotype in OMIM or Gene2Phenotype. - PMID: 33268356 (2020) - De novo missense variants identified in 13 unrelated individuals with a shared phenotype of GDD/ID, usually severe and often progressive, with mostly minor congenital anomalies. 8/13 patients showed abnormalities on brain MRI including hypomyelination (5), cortical atrophy (4), arachnoid cysts (3), and a thin corpus collosum (2). Variable seizure phenotypes were reported in 6/13 cases, all early-onset where specified, mostly during infancy (latest onset at 10 years of age).; to: Currently not associated with any phenotype in OMIM or Gene2Phenotype. - PMID: 33268356 (2020) - De novo missense variants identified in 13 unrelated individuals with a shared phenotype of GDD/ID, usually severe and often progressive, with mostly minor congenital anomalies. One individual was reported to have a normal IQ at 15 years. 8/13 patients showed abnormalities on brain MRI including hypomyelination (5), cortical atrophy (4), arachnoid cysts (3), and a thin corpus collosum (2). Variable seizure phenotypes were reported in 6/13 cases, all early-onset where specified, mostly during infancy (latest onset at 10 years of age). |
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| Intellectual disability - microarray and sequencing v3.655 | GATA6 |
Arina Puzriakova Added comment: Comment on list classification: Developmental delay has been reported in some patients with GATA6 variants. However, in view of the pancreatic and cardiac abnormalities that constitute the main phenotypes, cognitive impairment is unlikely to represent a key feature of the disease presentation. Maintaining Amber rating as the disorder is better represented in other panels (e.g. Diabetes, Severe Paediatric Disorders, etc) where this gene is already Green. |
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| Intellectual disability - microarray and sequencing v3.645 | ISCA-37418-Loss | Arina Puzriakova Phenotypes for Region: ISCA-37418-Loss were changed from Potocki-Lupski syndrome; hypotonia, poor feeding, failure to thrive, developmental delay particularly cognitive and language deficity, mild-moderate intellectual deficit, and neuropsychiatric disorders; Smith-Magenis syndrome; Structural cardiovascular anomalies (dilated aortic root, bicommissural aortic valve, atrial/ventricular and septal defects) and sleep disturbance; 182290; moderate intellectual disability, delayed speech and language skills, distinctive facial features, sleep disturbances, and behavioral problems; hypotonia, failure to thrive, mental retardation, pervasive developmental disorders, congenital anomalies; Dental abnormalities to Smith-Magenis syndrome, OMIM:182290; Smith-Magenis syndrome, MONDO:0008434 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.644 | EMC10 |
Zornitza Stark gene: EMC10 was added gene: EMC10 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: EMC10 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: EMC10 were set to 32869858 Phenotypes for gene: EMC10 were set to Intellectual disability Review for gene: EMC10 was set to RED Added comment: Homozygous variants of EMC1 are associated with GDD, scoliosis, and cerebellar atrophy, indicating the relevance of this pathway for neurogenetic disorders. One Saudi family with 2 affected individuals with mild ID, speech delay, and GDD. WES and Sanger sequencing revealed a homozygous splice acceptor site variant (c.679‐1G>A) in EMC10 . Variant segregated within the family. RT‐qPCR showed a substantial decrease in the relative EMC10 gene expression in the patients. Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.484 | PRKACB |
Konstantinos Varvagiannis gene: PRKACB was added gene: PRKACB was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: PRKACB was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: PRKACB were set to 33058759 Phenotypes for gene: PRKACB were set to Postaxial hand polydactyly; Postaxial foot polydactyly; Common atrium; Atrioventricular canal defect; Narrow chest; Abnormality of the teeth; Intellectual disability Penetrance for gene: PRKACB were set to unknown Mode of pathogenicity for gene: PRKACB was set to Loss-of-function variants (as defined in pop up message) DO NOT cause this phenotype - please provide details in the comments Review for gene: PRKACB was set to AMBER Added comment: ID was a feature in 2/4 individuals with PRKACB pathogenic variant reported to date. Please consider inclusion of PRKACB (and PRKACA) in other relevant gene panels e.g. for polydactyly, congenital heart defects. The disorder may be considered in the DD of ciliopathies. ----- Palencia-Campos et al (2020 - PMID: 33058759) report on the phenotype of 3 individuals heterozygous for PRKACA and 4 individuals heterozygous for PRKACB pathogenic variants. The most characteristic features in all individuals with PRKACA/PRKACB mutation, included postaxial polydactyly of hands (6/7 bilateral, 1/7 unilateral) and feet (4/7 bilateral, 1/7 unilateral), brachydactyly and congenital heart defects (CHD 5/7) namely a common atrium or AVSD. Two individuals with PRKACA variant who did not have CHD had offspring with the same variant and an AVSD. Other variably occurring features included short stature, limbs, narrow chest, abnormal teeth, oral frenula, nail dysplasia. One individual with PRKACB variant presented tumors. Intellectual disability was reported in 2/4 individuals with PRKACB variant (1/4: mild, 1/4: severe). The 3 individuals with PRKACA variant did not present ID. As the phenotype was overall suggestive of Ellis-van Creveld syndrome (or the allelic Weyers acrofacial dysostosis), although these diagnoses were ruled out following analysis of EVC and EVC2 genes. WES was carried out in all. PRKACA : A single heterozygous missense variant was identified in 3 individuals from 3 families (NM_002730.4:c.409G>A / p.Gly137Arg) with 1 of the probands harboring the variant in mosaic state (28% of reads) and having 2 similarly affected offspring. The variant was de novo in one individual and inherited in a third one having a similarly affected fetus (narrow thorax, postaxial polyd, AVSD). PRKACB : 4 different variants were identified (NM_002731.3: p.His88Arg/Asn, p.Gly235Arg, c.161C>T - p.Ser54Leu). One of the individuals was mosaic for the latter variant, while in all other cases the variant had occurred de novo. Protein kinase A (PKA) is a tetrameric holoenzyme formed by the association of 2 catalytic (C) subunits with a regulatory (R) subunit dimer. Activation of PKA is achieved through binding of 2 cAMP molecules to each R-subunit, and unleashing(/dissociation) of C-subunits to engage substrates. PRKACA/B genes encode the Cα- and Cβ-subunits while the 4 functionally non-redundant regulatory subunits are encoded by PRKAR1A/1B/2A/2B genes. The authors provide evidence that the variants confer increased sensitivity of PKA holoenzymes to activation by cAMP (compared to wt). By performing ectopic expression of wt or mt PRKACA/B (variants studied : PRKACA p.Gly137Arg / PRKACB p.Gly235Arg) in NIH 3T3 fibroblasts, the authors demonstrate that inhibition of hedgehog signaling likely underlyies the developmental defects observed in affected individuals. As for PRKACA, the authors cite another study where a 31-month old female with EvC syndrome diagnosis was found to harbor the aforementioned variant (NM_001304349.1:c.637G>A:p.Gly213Arg corresponding to NM_002730.4:c.409G>A / p.Gly137Arg) as a de novo event. Without additional evidence at the time, the variant was considered to be a candidate for this subject's phenotype (Monies et al 2019 – PMID: 31130284). Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.420 | SHMT2 |
Konstantinos Varvagiannis gene: SHMT2 was added gene: SHMT2 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: SHMT2 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: SHMT2 were set to 33015733 Phenotypes for gene: SHMT2 were set to Congenital microcephaly; Infantile axial hypotonia; Spastic paraparesis; Global developmental delay; Intellectual disability; Abnormality of the corpus callosum; Abnormal cortical gyration; Hypertrophic cardiomyopathy; Abnormality of the face; Proximal placement of thumb; 2-3 toe syndactyly Penetrance for gene: SHMT2 were set to Complete Review for gene: SHMT2 was set to GREEN Added comment: García‑Cazorla et al. (2020 - PMID: 33015733) report 5 individuals (from 4 families) with a novel brain and heart developmental syndrome caused by biallelic SHMT2 pathogenic variants. All affected subjects presented similar phenotype incl. microcephaly at birth (5/5 OFC < -2 SD though in 2/5 cases N OFC was observed later), DD and ID (1/5 mild-moderate, 1/5 moderate, 3/5 severe), motor dysfunction in the form of spastic (5/5) paraparesis, ataxia/dysmetria (3/4), intention tremor (in 3/?) and/or peripheral neuropathy (2 sibs). They exhibited corpus callosum hypoplasia (5/5) and perisylvian microgyria-like pattern (4/5). Cardiac problems were reported in all, with hypertrophic cardiomyopathy in 4/5 (from 3 families) and atrial-SD in the 5th individual (1/5). Common dysmorphic features incl. long palpebral/fissures, eversion of lateral third of lower eylids, arched eyebrows, long eyelashes, thin upper lip, short Vth finger, fetal pads, mild 2-3 toe syndactyly, proximally placed thumbs. Biallelic variants were identified following exome sequencing in all (other investigations not mentioned). Identified variants were in all cases missense SNVs or in-frame del, which together with evidence from population databases and mouse model might suggest a hypomorphic effect of variants and intolerance/embryonic lethality for homozygous LoF ones. SHMT2 encodes the mitohondrial form of serine hydroxymethyltransferase. The enzyme transfers one-carbon units from serine to tetrahydrofolate (THF) and generates glycine and 5,10,methylene-THF. Mitochondrial defect was suggested by presence of ragged red fibers in myocardial biopsy of one patient. Quadriceps and myocardial biopsies of the same individual were overall suggestive of myopathic changes. While plasma metabolites were within N range and SHMT2 protein levels not significantly altered in patient fibroblasts, the authors provide evidence for impaired enzymatic function eg. presence of the SHMT2 substrate (THF) in patient but not control (mitochondria-enriched) fibroblasts , decrease in glycine/serine ratios, impared folate metabolism. Patient fibroblasts displayed impaired oxidative capacity (reduced ATP levels in a medium without glucose, diminished oxygen consumption rates). Mitochondrial membrane potential and ROS levels were also suggestive of redox malfunction. Shmt2 ko in mice was previously shown to be embryonically lethal attributed to severe mitochondrial respiration defects, although there was no observed brain metabolic defect. The authors performed Shmt2 knockdown in motoneurons in Drosophila, demonstrating neuromuscular junction (# of satellite boutons) and motility defects (climbing distance/velocity). Overall this gene can be considered for inclusion with (probably) green rating in gene panels for ID, metabolic / mitochondrial disorders, cardiomyopathy, congenital microcephaly, corpus callosum anomalies, etc. Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.405 | NUP214 |
Eleanor Williams changed review comment from: Associated with {Encephalopathy, acute, infection-induced, susceptibility to, 9} 618426 in OMIM and Gene2Phenotype (probable). PMID: 31178128 - Fichtman et al 2019 - report on two families. Family A have first-cousin parents of Palestinian descent. The proband exhibited minor developmental delay from infancy, presented with ataxia, mental retardation, and intractable epilepsy and died at 11 years. He suffered deterioration in association with febrile illnesses. His cousin presented at 5.5 months with partially reversible encephalopathy and developmental regression after a febrile illness. Family B were sisters born to non-consanguineous parents of Northern European (non-Finnish) descent. The older sister had nystagmus at 2 months and mild hypotonia, but she was otherwise meeting milestones appropriately . At 15 months of age, she developed a fever that led to a rapid neurological decline, seizures, and abnormal movements. The younger sister presented at 7 months with failure to thrive and hyponatremia but was meeting developmental milestones appropriately. By 24 months of age, she had motor and speech delay, ataxic gait, and occasional very mild head bobbing. In family A a homozygous NUP214 p.Arg38Cys variant segregated with the disease in available family members. In family B the sisters were found to be compound heterozygous for a frameshift and a missense variant in NUP214 (p.Pro387Ser and p.Pro525Leufs∗6).; to: Associated with {Encephalopathy, acute, infection-induced, susceptibility to, 9} 618426 in OMIM and Gene2Phenotype (probable). PMID: 31178128 - Fichtman et al 2019 - report on two families one of Palestinian decent, the other Northern European (not Finnish descent). Each had two affected siblings in which neurological decline was seen after febrile events. The older son in family A, exhibited minor developmental delay from infancy. A homozygous missense variant was identified in NUP214 (p.Arg38Cys) in family A and segregated with the disease in available family members. In family B affected sisters were compound heterozygous for a frameshift and a missense variant in NUP214 (p.Pro387Ser and p.Pro525Leufs∗6). Functional studies with fibroblasts from one patient in family A showed a decrease in NUP214 and NUP88 levels compared to controls, PMID: 30758658 - Shamseldin et al 2019 - describe a multiplex consanguineous family in which four affected members presented with severe neonatal hypotonia, profound global developmental delay, progressive microcephaly and early death. Whole exome sequencing revealed the presence of a novel homozygous missense variant in NUP214, p.D154G. PMID: 29483668 - Egloff et al 2018 - report a 4-year-old girl presenting with developmental delay, growth retardation and facial dysmorphism. She was found to have a 9q deletion inherited from her healthy mother and a a hemizygous one-base pair deletion in the NUP214 gene inherited from her father. From patient leukocytes it was found that the expression level of the NUP214 transcript was significantly decreased and close to zero in the patient compared to the controls. |
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| Intellectual disability - microarray and sequencing v3.370 | STS | Arina Puzriakova Added comment: Comment on publications: Added publication (PMID: 32139392) describing psychiatric/behavioural phenotypes in patients with ichthyosis caused by X-linked deletions spanning STS. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.369 | NEMF |
Konstantinos Varvagiannis changed review comment from: Martin et al (2020 - PMID:32934225) report on 8 individuals from 6 families with a juvenile neuromuscular disease due to biallelic NEMF variants. (In one of these 8 cases it could not be ruled out that a de novo and maternally inherited variant were on the same allele, as phase was not determined). A ninth individual with similar presentation was found to harbor a single NEMF missense SNV as de novo event (due to a speculated dominant-negative effect). This individual had a similar presentation. Features incl. hypotonia (4/8 with biallelic variant (B) | 1/1 monoallelic (M) ), DD/ID (7/8B | 0/1M) with speech delay as universal feature (8/8B | 1/1M), axonal neuropathy (3/3B | 1/1M), ataxia (3/8B | 0/1M). Other findings included tremor (1/7B | 1/1M), abnormal brain imaging (2/6B / ?/1M), kyphosis/scoliosis (4/8B | 0/1M), respiratory distress (1/8B | 0/1M). NEMF (Rqc2 in yeast) encodes the nuclear export mediator factor, a component of the Ribosome-associated Quality Control (RCQ) complex which is involved in proteolytic targeting of incomplete polypeptides prodduced by ribosome stalling. NEMF facilitates the recruitment of E3 ligase Listerin (LTN1) which ubiquitinates nascent polypeptide chains for subsequent proteasomal degradation. The author provide evidence that mice homozygous for Nemf missense mutations display progressive motor phenotypes, exhibit neurogenic atrophy and progressive axonal degeneration. A further NEMF-null mouse model displayed more severe phenotype (with heterozygous mice being unaffected). Equivalent mutations (of those in the above mouse model) in yeast (Rqc2) were shown to interfere with its ability to modify aberrant translation products with C-terminal tails which assist RQC-mediated protein degradation. Mutation of Ltn1 (belonging to the same protein control pathway) has been also shown to lead to neurodegeneration im mice. Overall NEMF is thought to play a role in neuronal translational homeostasis and the disorder to be mediated by dysfunction of the RQC pathway (normally protecting neurons against degeneration). Sources: Literature; to: Martin et al (2020 - PMID:32934225) report on 8 individuals from 6 families with a juvenile neuromuscular disease due to biallelic NEMF variants. (In one of these 8 cases it could not be ruled out that a de novo and maternally inherited variant were on the same allele, as phase was not determined). A ninth individual with similar presentation was found to harbor a single NEMF missense SNV as de novo event (due to a speculated dominant-negative effect). This individual had a similar presentation. Features incl. hypotonia (4/8 with biallelic variant (B) | 1/1 monoallelic (M) ), DD/ID (7/8B | 0/1M) with speech delay as universal feature (8/8B | 1/1M), axonal neuropathy (3/3B | 1/1M), ataxia (3/8B | 0/1M). Other findings included tremor (1/7B | 1/1M), abnormal brain imaging (2/6B / ?/1M), kyphosis/scoliosis (4/8B | 0/1M), respiratory distress (1/8B | 0/1M). NEMF (Rqc2 in yeast) encodes the nuclear export mediator factor, a component of the Ribosome-associated Quality Control (RCQ) complex which is involved in proteolytic targeting of incomplete polypeptides produced by ribosome stalling. NEMF facilitates the recruitment of E3 ligase Listerin (LTN1) which ubiquitinates nascent polypeptide chains for subsequent proteasomal degradation. The author provide evidence that mice homozygous for Nemf missense mutations display progressive motor phenotypes, exhibit neurogenic atrophy and progressive axonal degeneration. A further NEMF-null mouse model displayed more severe phenotype (with heterozygous mice being unaffected). Equivalent mutations (of those in the above mouse model) in yeast (Rqc2) were shown to interfere with its ability to modify aberrant translation products with C-terminal tails which assist RQC-mediated protein degradation. Mutation of Ltn1 (belonging to the same protein control pathway) has been also shown to lead to neurodegeneration in mice. Overall NEMF is thought to play a role in neuronal translational homeostasis and the disorder to be mediated by dysfunction of the RQC pathway (normally protecting neurons against degeneration). Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.369 | NEMF |
Konstantinos Varvagiannis changed review comment from: Martin et al (2020 - PMID:32934225) report on 8 individuals from 6 families with a juvenile neuromuscular disease due to biallelic NEMF variants. (In one of these 8 cases it could be ruled out that the de novo and maternally inherited variants were on the same allele, as phase was not been determined). A ninth individual with similar presentation was found to harbor a single NEMF missense SNV as de novo event (due to a speculated dominant-negative effect). This individual had a similar presentation. Features incl. hypotonia (4/8 with biallelic variant (B) | 1/1 monoallelic (M) ), DD/ID (7/8B | 0/1M) with speech delay as universal feature (8/8B | 1/1M), axonal neuropathy (3/3B | 1/1M), ataxia (3/8B | 0/1M). Other findings included tremor (1/7B | 1/1M), abnormal brain imaging (2/6B / ?/1M), kyphosis/scoliosis (4/8B | 0/1M), respiratory distress (1/8B | 0/1M). NEMF (Rqc2 in yeast) encodes the nuclear export mediator factor, a component of the Ribosome-associated Quality Control (RCQ) complex which is involved in proteolytic targeting of incomplete polypeptides prodduced by ribosome stalling. NEMF facilitates the recruitment of E3 ligase Listerin (LTN1) which ubiquitinates nascent polypeptide chains for subsequent proteasomal degradation. The author provide evidence that mice homozygous for Nemf missense mutations display progressive motor phenotypes, exhibit neurogenic atrophy and progressive axonal degeneration. A further NEMF-null mouse model displayed more severe phenotype (with heterozygous mice being unaffected). Equivalent mutations (of those in the above mouse model) in yeast (Rqc2) were shown to interfere with its ability to modify aberrant translation products with C-terminal tails which assist RQC-mediated protein degradation. Mutation of Ltn1 (belonging to the same protein control pathway) has been also shown to lead to neurodegeneration im mice. Overall NEMF is thought to play a role in neuronal translational homeostasis and the disorder to be mediated by dysfunction of the RQC pathway (normally protecting neurons against degeneration). Sources: Literature; to: Martin et al (2020 - PMID:32934225) report on 8 individuals from 6 families with a juvenile neuromuscular disease due to biallelic NEMF variants. (In one of these 8 cases it could not be ruled out that a de novo and maternally inherited variant were on the same allele, as phase was not determined). A ninth individual with similar presentation was found to harbor a single NEMF missense SNV as de novo event (due to a speculated dominant-negative effect). This individual had a similar presentation. Features incl. hypotonia (4/8 with biallelic variant (B) | 1/1 monoallelic (M) ), DD/ID (7/8B | 0/1M) with speech delay as universal feature (8/8B | 1/1M), axonal neuropathy (3/3B | 1/1M), ataxia (3/8B | 0/1M). Other findings included tremor (1/7B | 1/1M), abnormal brain imaging (2/6B / ?/1M), kyphosis/scoliosis (4/8B | 0/1M), respiratory distress (1/8B | 0/1M). NEMF (Rqc2 in yeast) encodes the nuclear export mediator factor, a component of the Ribosome-associated Quality Control (RCQ) complex which is involved in proteolytic targeting of incomplete polypeptides prodduced by ribosome stalling. NEMF facilitates the recruitment of E3 ligase Listerin (LTN1) which ubiquitinates nascent polypeptide chains for subsequent proteasomal degradation. The author provide evidence that mice homozygous for Nemf missense mutations display progressive motor phenotypes, exhibit neurogenic atrophy and progressive axonal degeneration. A further NEMF-null mouse model displayed more severe phenotype (with heterozygous mice being unaffected). Equivalent mutations (of those in the above mouse model) in yeast (Rqc2) were shown to interfere with its ability to modify aberrant translation products with C-terminal tails which assist RQC-mediated protein degradation. Mutation of Ltn1 (belonging to the same protein control pathway) has been also shown to lead to neurodegeneration im mice. Overall NEMF is thought to play a role in neuronal translational homeostasis and the disorder to be mediated by dysfunction of the RQC pathway (normally protecting neurons against degeneration). Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.369 | NEMF |
Konstantinos Varvagiannis changed review comment from: Martin et al (2020 - PMID:32934225) report on 8 individuals from 6 families with a juvenile neuromuscular disease due to biallelic NEMF variants. A ninth individual with similar presentation was found to harbor a single NEMF missense SNV as de novo event (due to a speculated dominant-negative effect). This individual had a similar presentation. Features incl. hypotonia (4/8 with biallelic variant (B) | 1/1 monoallelic (M) ), DD/ID (7/8B | 0/1M) with speech delay as universal feature (8/8B | 1/1M), axonal neuropathy (3/3B | 1/1M), ataxia (3/8B | 0/1M). Other findings included tremor (1/7B | 1/1M), abnormal brain imaging (2/6B / ?/1M), kyphosis/scoliosis (4/8B | 0/1M), respiratory distress (1/8B | 0/1M). NEMF (Rqc2 in yeast) encodes the nuclear export mediator factor, a component of the Ribosome-associated Quality Control (RCQ) complex which is involved in proteolytic targeting of incomplete polypeptides prodduced by ribosome stalling. NEMF facilitates the recruitment of E3 ligase Listerin (LTN1) which ubiquitinates nascent polypeptide chains for subsequent proteasomal degradation. The author provide evidence that mice homozygous for Nemf missense mutations display progressive motor phenotypes, exhibit neurogenic atrophy and progressive axonal degeneration. A further NEMF-null mouse model displayed more severe phenotype (with heterozygous mice being unaffected). Equivalent mutations (of those in the above mouse model) in yeast (Rqc2) were shown to interfere with its ability to modify aberrant translation products with C-terminal tails which assist RQC-mediated protein degradation. Mutation of Ltn1 (belonging to the same protein control pathway) has been also shown to lead to neurodegeneration im mice. Overall NEMF is thought to play a role in neuronal translational homeostasis and the disorder to be mediated by dysfunction of the RQC pathway (normally protecting neurons against degeneration). Sources: Literature; to: Martin et al (2020 - PMID:32934225) report on 8 individuals from 6 families with a juvenile neuromuscular disease due to biallelic NEMF variants. (In one of these 8 cases it could be ruled out that the de novo and maternally inherited variants were on the same allele, as phase was not been determined). A ninth individual with similar presentation was found to harbor a single NEMF missense SNV as de novo event (due to a speculated dominant-negative effect). This individual had a similar presentation. Features incl. hypotonia (4/8 with biallelic variant (B) | 1/1 monoallelic (M) ), DD/ID (7/8B | 0/1M) with speech delay as universal feature (8/8B | 1/1M), axonal neuropathy (3/3B | 1/1M), ataxia (3/8B | 0/1M). Other findings included tremor (1/7B | 1/1M), abnormal brain imaging (2/6B / ?/1M), kyphosis/scoliosis (4/8B | 0/1M), respiratory distress (1/8B | 0/1M). NEMF (Rqc2 in yeast) encodes the nuclear export mediator factor, a component of the Ribosome-associated Quality Control (RCQ) complex which is involved in proteolytic targeting of incomplete polypeptides prodduced by ribosome stalling. NEMF facilitates the recruitment of E3 ligase Listerin (LTN1) which ubiquitinates nascent polypeptide chains for subsequent proteasomal degradation. The author provide evidence that mice homozygous for Nemf missense mutations display progressive motor phenotypes, exhibit neurogenic atrophy and progressive axonal degeneration. A further NEMF-null mouse model displayed more severe phenotype (with heterozygous mice being unaffected). Equivalent mutations (of those in the above mouse model) in yeast (Rqc2) were shown to interfere with its ability to modify aberrant translation products with C-terminal tails which assist RQC-mediated protein degradation. Mutation of Ltn1 (belonging to the same protein control pathway) has been also shown to lead to neurodegeneration im mice. Overall NEMF is thought to play a role in neuronal translational homeostasis and the disorder to be mediated by dysfunction of the RQC pathway (normally protecting neurons against degeneration). Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.369 | NEMF |
Konstantinos Varvagiannis gene: NEMF was added gene: NEMF was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: NEMF was set to BOTH monoallelic and biallelic, autosomal or pseudoautosomal Publications for gene: NEMF were set to 32934225 Phenotypes for gene: NEMF were set to Hypotonia; Global developmental delay; Intellectual disability; Axonal neuropathy; Ataxia; Abnormal brain imaging; Kyphosis; Scoliosis; Tremor; Respiratory distress Penetrance for gene: NEMF were set to Complete Review for gene: NEMF was set to GREEN Added comment: Martin et al (2020 - PMID:32934225) report on 8 individuals from 6 families with a juvenile neuromuscular disease due to biallelic NEMF variants. A ninth individual with similar presentation was found to harbor a single NEMF missense SNV as de novo event (due to a speculated dominant-negative effect). This individual had a similar presentation. Features incl. hypotonia (4/8 with biallelic variant (B) | 1/1 monoallelic (M) ), DD/ID (7/8B | 0/1M) with speech delay as universal feature (8/8B | 1/1M), axonal neuropathy (3/3B | 1/1M), ataxia (3/8B | 0/1M). Other findings included tremor (1/7B | 1/1M), abnormal brain imaging (2/6B / ?/1M), kyphosis/scoliosis (4/8B | 0/1M), respiratory distress (1/8B | 0/1M). NEMF (Rqc2 in yeast) encodes the nuclear export mediator factor, a component of the Ribosome-associated Quality Control (RCQ) complex which is involved in proteolytic targeting of incomplete polypeptides prodduced by ribosome stalling. NEMF facilitates the recruitment of E3 ligase Listerin (LTN1) which ubiquitinates nascent polypeptide chains for subsequent proteasomal degradation. The author provide evidence that mice homozygous for Nemf missense mutations display progressive motor phenotypes, exhibit neurogenic atrophy and progressive axonal degeneration. A further NEMF-null mouse model displayed more severe phenotype (with heterozygous mice being unaffected). Equivalent mutations (of those in the above mouse model) in yeast (Rqc2) were shown to interfere with its ability to modify aberrant translation products with C-terminal tails which assist RQC-mediated protein degradation. Mutation of Ltn1 (belonging to the same protein control pathway) has been also shown to lead to neurodegeneration im mice. Overall NEMF is thought to play a role in neuronal translational homeostasis and the disorder to be mediated by dysfunction of the RQC pathway (normally protecting neurons against degeneration). Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.360 | SETD1A | Zerin Hyder reviewed gene: SETD1A: Rating: GREEN; Mode of pathogenicity: None; Publications: 32346159; Phenotypes: Epilepsy, early-onset, with or without developmental delay, craniofacial dysmorphisms, behavioural/psychiatric abnormalities; Mode of inheritance: MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.255 | TAF1C |
Konstantinos Varvagiannis gene: TAF1C was added gene: TAF1C was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: TAF1C was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: TAF1C were set to 32779182 Phenotypes for gene: TAF1C were set to Global developmental delay; Intellectual disability; Spasticity; Strabismus; Seizures; Abnormality of nervous system morphology Penetrance for gene: TAF1C were set to Complete Review for gene: TAF1C was set to AMBER Added comment: Knuutinen et al (2020 - PMID: 32779182) report on 2 individuals from 2 consanguineous families, homozygous for TAF1C missense variants. Both presented with an early onset neurological phenotype with severe global DD, ID (2/2 - moderate and profound), spasticity (2/2), ophthalmic findings (strabismus 2/2, nystagmus 1/2). Epilepsy, abnormal brain MRI (cerebral and cerebellar atrophy and white matter hyperintensities) as well and additional findings were reported in one (always the same individual). Following a normal CMA, exome in the first case revealed a homozygous missense SNV (NM_005679.3:c.1165C>T / p.Arg389Cys) supported by in silico predictions. mRNA and protein levels were substantially reduced in fibroblasts from this subject. Only the patient and parents were tested for the variant but not 3 unaffected sibs (fig1). The second individual was homozygous for another missense variant (p.Arg405Cys) also supported by in silico predictions. The girl was the single affected person within the family with an unaffected sib and parents heterozygous for the variant. Several other unaffected relatives in the extended pedigree were either carriers for this variant or homozygous for the wt allele. TAF1C encodes the TATA-box binding protein associated factor (TAF) RNA polymerase I subunit. RNA polymerase I (Pol I) transcribes genes to produce rRNA. For Pol I to initiate transcription, two transcription factors are required : UBF (upstream binding factor encoded by UBTF) and SL1 (selectivity factor 1). The latter is formed by TBP (TATA-binding protein) and 3 Pol I-specific TBP-associated factors (TAFs). A recurrent de novo missense variant in UBTF (encoding the other Pol I transcription factor) causes a disorder with highly similar features. The specific variant acts through a gain-of-function mechanism (and not by LoF which appears to apply for TAF1C based on expression data). The authors hypothesize that altered Pol I activity and resulting ribosomal stress could cause the microcephaly and leukodystrophy (both reported in 1 - the same - individual). As a result, TAF1C may be considered for inclusion in the ID panel with amber rating pending further evidence. Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.234 | OXR1 | Sarah Leigh Added comment: Comment on list classification: Associated with relevant phenotype in OMIM and as probable Gen2Phen gene for Autosomal-Recessive Neurological Disease with Cerebellar Atrophy and Lysosomal Dysfunction. At least 4 variants reported in at least 3 unrelated cases, who all had epilepsy and global developmental delay. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.234 | OXR1 | Sarah Leigh Added comment: Comment on list classification: Associated with relevant phenotype in OMIM and as probable Gen2Phen gene for Autosomal-Recessive Neurological Disease with Cerebellar Atrophy and Lysosomal Dysfunction. At least 4 variants reported in at least 3 unrelated cases, who all had epilepsy and global developmental delay. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.232 | OXR1 | Sarah Leigh Phenotypes for gene: OXR1 were changed from Central hypotonia; Global developmental delay; Delayed speech and language development; Intellectual disability; Seizures; Abnormality of the cerebellum to Cerebellar hypoplasia/atrophy, epilepsy, and global developmental delay 213000 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.219 | ZNF407 |
Konstantinos Varvagiannis gene: ZNF407 was added gene: ZNF407 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: ZNF407 was set to BOTH monoallelic and biallelic, autosomal or pseudoautosomal Publications for gene: ZNF407 were set to 24907849; 32737394; 23195952 Phenotypes for gene: ZNF407 were set to Global developmental delay; Intellectual disability Penetrance for gene: ZNF407 were set to unknown Review for gene: ZNF407 was set to AMBER Added comment: You may consider inclusion of this gene probably with amber rating (or green if the evidence for biallelic variants is considered sufficient). Biallelic variants: - Kambouris et al. (2014 - PMID: 24907849) described 2 brothers with severe DD and ID, born to first cousin parents. Homozygosity mapping, following other non-diagnostic investigations (incl. aCGH), revealed 4 major homozygosity intervals. Exome sequencing in one identified 5 variants within these intervals, ZNF407 (c.5054C>G, p.Ser1685Trp) being the best candidate, supported also by segregation studies. The authors commented that zinc finger proteins act as transcriptional regulators, with mutations in genes encoding for other zinc finger proteins interfering with normal brain development. - Zahra et al. (2020 - PMID: 32737394) report on 7 affected individuals (from 3 families) homozygous or compound heterozygous for ZNF407 variants. Features included hypotonia, DD and ID (in all) and variable occurrence of short stature (6/6), microcephaly (in at least 5), behavioural, visual problems and deafness. Linkage analysis in the first family revealed a 4.4 Mb shared homozygosity region and exome (30x) revealed a 3-bp duplication, confirmed by Sanger sequencing and segregating with the disease (NM_001146189:c.2814_2816dup, p.Val939dup). Affected subjects from the 2 other families were each found to be homozygous (c.2405G>T) or compound heterozygous (c.2884C>G, c.3642G>C) for other variants. Segregation was compatible in all families. Other studies were not performed. The authors comment than only the 3-bp duplication fulfilled ACMG criteria for classification as LP, the other variants being all formally classified as VUS (also due to in silico predictions predicting a LB effect). In addition, while several features such as DD/ID and short stature appeared to be frequent among all patients reported, Zahra et all comment that there was partial clinical overlap with the sibs described by Kambouris et al (additional variants?). Monoallelic disruption of ZNF407: - Ren et al (2013 - PMID: 23195952) described an 8 y.o. boy with ID and ASD. The boy was found to harbor a de novo translocation between chromosomes 3 and 18 [46,XY,t(3;18)(p13;q22.3)]. Array CGH did not reveal any P/LP CNV. Delineation of the breakpoints (FISH, long-range PCR) revealed that the chr18 breakpoint disrupted intron 3 of ZNF407 (isoform 1) with the other breakpoint within a gene-free region of exon 3. There was a loss of 4-8 nt in chr18 and 2-6 in chr3. Sequencing of ZNF407 did not reveal additional variants. RNA isolation in blood followed by RT-PCR studied expression of all 3 ZNF407 isoforms (the intronic region being shared by isoforms 1 and 2). Expression of isoform 1 was shown to be significantly reduced compared to controls. Isoform 2 was undetectable (in blood) while isoform 3 expression was similar to controls. Sequencing of 105 additional patients with similar clinical presentation (ID & ASD) revealed 2 further individuals with de novo missense variants. - Based on the discussion by Kambouris et al (PMID: 24907849 - cited literature not here reviewed) ZNF407 may be deleted in patients with congenital aural atresia due to deletion of a critical region of 18q22.3 (though TSHZ1 is responsible for this phenotype) or 18q- although such deletions span several other genes (cited PMID: 16639285). In one case the breakpoint was shown to be disrupting ZNF407 (cited PMID: 24092497). - The denovo db and Decipher (research variant tab) list few individuals with de novo ZNF407 SNVs although these do not seem to allow conclusions. https://denovo-db.gs.washington.edu/denovo-db/QueryVariantServlet?searchBy=Gene&target=ZNF407 https://decipher.sanger.ac.uk/search/ddd-research-variants/results?q=znf407 Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.185 | DNM1L |
Arina Puzriakova changed review comment from: Associated with related phenotype in OMIM and 'probable' gene in G2P. Variants in DNM1L cause a chronic neurological disorder, which is commonly associated with neonatal lethality. Global developmental delay or cognitive impairment (mild-profound) is reported in several surviving patients: PMID: 26931468 - Two unrelated cases: A male with global developmental delay, hypotonia and status epilepticus. WES revealed a c.1048G>A, p.G350R variant, for which low-level (68%) mosaicism was detected in the maternal sample.; to: Associated with related phenotype in OMIM and 'probable' gene in G2P. Variants in DNM1L cause a chronic neurological disorder, which is commonly associated with neonatal lethality. Global developmental delay or cognitive impairment (mild-profound) is reported in several surviving patients: PMID: 26931468 - Two unrelated cases: A male with global developmental delay, hypotonia and status epilepticus. WES revealed a c.1048G>A, p.G350R variant, for which low-level (6–8%) mosaicism was detected in the maternal sample. The second patient, with diffuse hypotonia, global developmental delay, poor growth, and persistent elevation of lactate, was found to harbour a de novo DNM1L variant (c.1135G>A, p.E379K). However, another de novo change in the PDHA1 gene (c.448G>A, p.G150R) was also found, and the definitive contribution of each variant to the patients phenotype could not be ascertained. PMID: 27328748 - Compound heterozygous DNM1L variants (c.106A>G, p.Ser36Gly; c.346_347delGA, p.Glu116Lysfs*6) identified in two brothers (3 and 16-years-old) with psychomotor delay, ocular and cerebellar involvement, including mild cognitive impairment in the older brother. Some supporting functional evidence using patient fibroblasts and a yeast model. PMID: 27301544 - De novo missense variant (c.1217T>C, p.Leu406Ser) identified in a child who presented severe hypotonia, infantile spasms with suppression‐burst and a high level of lactate in CSF. Development was profoundly delayed, and he attained no developmental milestones before his death at 18 months of age. PMID: 26604000 - De novo missense substitution, (c.1085G>A; p.Gly362Asp) identified in a child with refractory epilepsy. Profound global developmental delay was reported, and at the last clinical assessment (age 7 years), he remained nonambulatory with the use of <10 monosyllabic words. PMID: 26992161 - De novo heterozygous c.1084G>A (p.Gly362Ser) variant. Developmental delay was reported from 6-months of age, and at 2-years-old he was said to not be able to utter any intelligible words. There are also reports of an identical de novo heterozygous missense variant (p.R403C) in four unrelated individuals who all experienced normal development until a sudden-onset episode of status epilepticus at the age of 4, 5, 10, and 11-years-old, respectively. Subsequently, all presented with rapid neurological regression, diffuse cerebral atrophy and substantial cognitive decline. Functional studies showed the variant confers a dominant negative effect (PMID: 27145208; 30767894; 30711678). |
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| Intellectual disability - microarray and sequencing v3.183 | DNM1L | Arina Puzriakova reviewed gene: DNM1L: Rating: GREEN; Mode of pathogenicity: ; Publications: 27145208, 30767894, 30711678, 26931468, 27328748, 27301544, 26604000, 26992161; Phenotypes: Epileptic encephalopathy, 614388, Global developmental delay, Cerebral atrophy, Microcephaly; Mode of inheritance: BOTH monoallelic and biallelic, autosomal or pseudoautosomal | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.174 | PTPN23 | Eleanor Williams Phenotypes for gene: PTPN23 were changed from Developmental epileptic encephalopathy with hypomyelination and brain atrophy; Intellectual disability; Severe developmental delay, to Developmental epileptic encephalopathy with hypomyelination and brain; Neurodevelopmental disorder and structural brain anomalies with or without seizures and spasticity MIM#618890 atrophy; Intellectual disability; Severe developmental delay, | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.169 | SEC31A | Sarah Leigh Phenotypes for gene: SEC31A were changed from Neurodevelopmental disorder with spastic quadriplegia, optic atrophy, seizures, and structural brain anomalies, OMIM #618651 to Neurodevelopmental disorder with spastic quadriplegia, optic atrophy, seizures, and structural brain anomalies 618651 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.127 | CAPZA2 |
Eleanor Williams gene: CAPZA2 was added gene: CAPZA2 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: CAPZA2 was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: CAPZA2 were set to 32338762 Review for gene: CAPZA2 was set to AMBER Added comment: Not associated with a disease phenotype in OMIM. PMID: 32338762 - Huang et al 2020 - report 2 unrelated families (Chinese and European) in which a de novo heterozygous variant has been identified in CAPZA2 in paediatric probands that present with global motor development delay, speech delay, intellectual disability, hypotonia. One proband had seizures at 7 months but these were controlled with medication and did not repeat. The other proband at age one had an atypical febrile seizure that was controlled without medication. Functional studies in Drosophila suggest that these variants are mild loss of function mutations but that they can act as dominant negative variants in actin polymerization in bristles. Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.126 | HARS |
Zornitza Stark changed review comment from: 3 cases from 2 unrelated families with biallelic variants and mild to severe intellectual disability as a feature of the condition. Please note association with Usher syndrome (deafness/retinal phenotypes) has been assessed as 'refuted' by ClinGen, and this gene has a well-established association between heterozygous variants and CMT. Sources: Literature; to: 3 cases from 2 unrelated families with biallelic variants and mild to severe intellectual disability as a feature of the condition. We have also added to paediatric ataxia panel as Amber. Please note association with Usher syndrome (deafness/retinal phenotypes) has been assessed as 'refuted' by ClinGen, and this gene has a well-established association between heterozygous variants and CMT. Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.126 | EXOC7 |
Zornitza Stark gene: EXOC7 was added gene: EXOC7 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: EXOC7 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: EXOC7 were set to 32103185 Phenotypes for gene: EXOC7 were set to brain atrophy; seizures; developmental delay; microcephaly Review for gene: EXOC7 was set to GREEN gene: EXOC7 was marked as current diagnostic Added comment: 4 families with 8 affected individuals with brain atrophy, seizures, and developmental delay, and in more severe cases microcephaly and infantile death. Four novel homozygous or comp.heterozygous variants found in EXOC7, which segregated with disease in the families. They showed that EXOC7, a member of the mammalian exocyst complex, is highly expressed in developing human cortex. In addition, a zebrafish model of Exoc7 deficiency recapitulates the human disorder with increased apoptosis and decreased progenitor cells during telencephalon development, suggesting that the brain atrophy in human cases reflects neuronal degeneration. We have added to the Microcephaly and Genetic Epilepsies panels as well. Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.99 | PIGK | Sarah Leigh Phenotypes for gene: PIGK were changed from Neurodevelopmental disorder with hypotonia and cerebellar atrophy, with or without seizures 618879 to Neurodevelopmental disorder with hypotonia and cerebellar atrophy, with or without seizures 618879 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.99 | PIGK | Sarah Leigh Phenotypes for gene: PIGK were changed from Neurodevelopmental disorder with hypotonia and cerebellar atrophy, with or without seizures 618879 to Neurodevelopmental disorder with hypotonia and cerebellar atrophy, with or without seizures 618879 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.98 | PIGK | Sarah Leigh Phenotypes for gene: PIGK were changed from Neurodevelopmental disorder with hypotonia and cerebellar atrophy, with or without seizures 618879 to Neurodevelopmental disorder with hypotonia and cerebellar atrophy, with or without seizures 618879 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.97 | PIGK | Sarah Leigh Phenotypes for gene: PIGK were changed from Neurodevelopmental disorder with hypotonia and cerebellar atrophy, with or without seizures 618879 to Neurodevelopmental disorder with hypotonia and cerebellar atrophy, with or without seizures 618879 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.95 | PIGK | Sarah Leigh Phenotypes for gene: PIGK were changed from Neurodevelopmental disorder with hypotonia and cerebellar atrophy, with or without seizures 618879 to Neurodevelopmental disorder with hypotonia and cerebellar atrophy, with or without seizures 618879 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.94 | PIGK | Sarah Leigh Phenotypes for gene: PIGK were changed from Neurodevelopmental disorder with hypotonia and cerebellar atrophy, with or without seizures 618879 to Neurodevelopmental disorder with hypotonia and cerebellar atrophy, with or without seizures 618879 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.93 | PIGK | Sarah Leigh Phenotypes for gene: PIGK were changed from Neurodevelopmental disorder with hypotonia and cerebellar atrophy, with or without seizures 618879 to Neurodevelopmental disorder with hypotonia and cerebellar atrophy, with or without seizures 618879 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.92 | PIGK | Sarah Leigh Phenotypes for gene: PIGK were changed from Intellectual disability; seizures; cerebellar atrophy to Neurodevelopmental disorder with hypotonia and cerebellar atrophy, with or without seizures 618879 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.68 | TRAPPC4 | Rebecca Foulger Phenotypes for gene: TRAPPC4 were changed from Feeding difficulties; Progressive microcephaly; Intellectual disability; Seizures; Spastic tetraparesis; Abnormality of the face; Scoliosis; Cortical visual impairment; Hearing impairment to Neurodevelopmental disorder with epilepsy, spasticity, and brain atrophy, 618741 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.57 | PCYT2 | Rebecca Foulger Phenotypes for gene: PCYT2 were changed from Global developmental delay; Developmental regression; Intellectual disability; Spastic paraparesis; Seizures; Spastic tetraparesis; Cerebral atrophy; Cerebellar atrophy to Spastic paraplegia 82, autosomal recessive, 618770; Global developmental delay; Developmental regression; Intellectual disability; Spastic paraparesis; Seizures; Spastic tetraparesis; Cerebral atrophy; Cerebellar atrophy | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.33 | VPS51 |
Zornitza Stark gene: VPS51 was added gene: VPS51 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: VPS51 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: VPS51 were set to 30624672; 31207318 Phenotypes for gene: VPS51 were set to Pontocerebellar hypoplasia, type 13, MIM# 618606 Review for gene: VPS51 was set to AMBER Added comment: Two families reported with bi-allelic variants in this gene and global developmental delay, impaired intellectual development with absent speech, microcephaly, and progressive atrophy of the cerebellar vermis and brainstem. Additional features, including seizures and visual impairment, are variable. Sources: Literature |
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| Intellectual disability - microarray and sequencing v3.24 | PIGK |
Zornitza Stark gene: PIGK was added gene: PIGK was added to Intellectual disability. Sources: Expert list Mode of inheritance for gene: PIGK was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: PIGK were set to 32220290 Phenotypes for gene: PIGK were set to Intellectual disability; seizures; cerebellar atrophy Review for gene: PIGK was set to GREEN gene: PIGK was marked as current diagnostic Added comment: 12 individuals from 9 unrelated families reported. Sources: Expert list |
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| Intellectual disability - microarray and sequencing v3.3 | MYH6 | Zornitza Stark reviewed gene: MYH6: Rating: RED; Mode of pathogenicity: None; Publications: ; Phenotypes: {Sick sinus syndrome 3} 614090 3 Atrial septal defect 3, MIM# 614089, Cardiomyopathy, dilated, 1EE, MIM# 613252, Cardiomyopathy, hypertrophic, 14, MIM# 613251; Mode of inheritance: MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.3 | TBX20 | Zornitza Stark reviewed gene: TBX20: Rating: RED; Mode of pathogenicity: None; Publications: ; Phenotypes: Atrial septal defect 4, MIM# 611363; Mode of inheritance: None | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.3 | SEC31A |
Zornitza Stark gene: SEC31A was added gene: SEC31A was added to Intellectual disability. Sources: Expert list Mode of inheritance for gene: SEC31A was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: SEC31A were set to 30464055 Phenotypes for gene: SEC31A were set to Neurodevelopmental disorder with spastic quadriplegia, optic atrophy, seizures, and structural brain anomalies, OMIM #618651 Review for gene: SEC31A was set to AMBER Added comment: Single family with two affected sibs with functional data (drosophila), one to watch. Sources: Expert list |
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| Intellectual disability - microarray and sequencing v3.0 | OXR1 | Zornitza Stark reviewed gene: OXR1: Rating: GREEN; Mode of pathogenicity: None; Publications: 31785787; Phenotypes: Intellectual disability, seizures, cerebellar atrophy; Mode of inheritance: BIALLELIC, autosomal or pseudoautosomal; Current diagnostic: yes | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.0 | KCNMA1 | Zornitza Stark reviewed gene: KCNMA1: Rating: GREEN; Mode of pathogenicity: Other; Publications: 27567911, 29545233, 26195193, 31427379; Phenotypes: Cerebellar atrophy, developmental delay, and seizures, MIM# 617643, Paroxysmal nonkinesigenic dyskinesia, 3, with or without generalized epilepsy, MIM#609446; Mode of inheritance: MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.0 | GJA1 | Zornitza Stark reviewed gene: GJA1: Rating: RED; Mode of pathogenicity: None; Publications: ; Phenotypes: Atrioventricular septal defect 3, MIM#600309, Craniometaphyseal dysplasia, autosomal recessive, MIM#218400, Erythrokeratodermia variabilis et progressiva 3, MIM#617525, Hypoplastic left heart syndrome 1, MIM#241550, Oculodentodigital dysplasia, MIM#164200, Oculodentodigital dysplasia, autosomal recessive, MIM#257850, Palmoplantar keratoderma with congenital alopecia, MIM#104100, Syndactyly, type III, MIM# 186100; Mode of inheritance: BOTH monoallelic and biallelic, autosomal or pseudoautosomal | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.0 | FAAH2 | Zornitza Stark reviewed gene: FAAH2: Rating: RED; Mode of pathogenicity: None; Publications: 25885783; Phenotypes: Neuropsychiatric disorder; Mode of inheritance: X-LINKED: hemizygous mutation in males, biallelic mutations in females | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.0 | CACNA2D2 | Zornitza Stark reviewed gene: CACNA2D2: Rating: GREEN; Mode of pathogenicity: None; Publications: ; Phenotypes: Cerebellar atrophy with seizures and variable developmental delay, MIM#618501; Mode of inheritance: BIALLELIC, autosomal or pseudoautosomal; Current diagnostic: yes | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.0 | BICD2 | Zornitza Stark reviewed gene: BICD2: Rating: RED; Mode of pathogenicity: None; Publications: ; Phenotypes: Spinal muscular atrophy, lower extremity-predominant, 2A, autosomal dominant, MIM#615290; Mode of inheritance: MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v3.0 | RARS |
Konstantinos Varvagiannis gene: RARS was added gene: RARS was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: RARS was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: RARS were set to 31814314; 28905880; 24777941 Phenotypes for gene: RARS were set to Cerebral hypomyelination; Global developmental delay; Intellectual disability; Seizures; Cerebral atrophy; Nystagmus; Ataxia; Feeding difficulties Penetrance for gene: RARS were set to Complete Review for gene: RARS was set to GREEN Added comment: Biallelic pathogenic RARS1 variants cause Leukodystrophy, hypomyelinating, 9 (# 616140). The current review was based primarily on PMID: 31814314 (Mendes et al, 2019) providing details on 20 affected individuals from 15 families. 5 of these patients were included in a previous publication (Wolf et al, 2014 - PMID: 24777941) sharing authors with this study. Clinical presentation and severity can be highly variable. However, among the 15 patients of relevant age (5/20 deceased at an early age), ID was observed in 13 (in 6/13 mild-moderate, in 7/13 severe/profound). Epilepsy was reported in half (10/20) with seizures being refractory to treatment in most and the phenotype corresponding to an infantile epileptic encephalopathy. DD and seizures were the presenting feature in 7 and 5 patients respectively, while in other cases presenting features were less specific (eg. failure to thrive in 1/20, irritabilty in 2/20). As a result the gene appears to be relevant to both DD/ID and epilepsy panels. RARS1 encodes the cytoplasmic arginyl-tRNA synthetase 1, which is a component of the aminoacyl-tRNA synthetase complex (OMIM and Wolf et al, 2014 - PMID: 24777941). Aminoacyl-tRNA synthetases catalyze the aminoacylation ('charging') of tRNA by (with) their cognate amino acid. Utilisation of alternative initiation codons, from a single mRNA transcript, results in translation of a long and a short protein isoform (Zheng et al 2006 - PMID: 16430231). The long isoform is needed for the formation of the multi-synthetase complex (MSC), while the short is free in the cytoplasm and does not have any interaction with the MSC. The long isoform appears to be essential for protein synthesis (discussed with several refs provided in PMID: 28905880 - Nafisinia et al, 2017). The role of variants has been supported in several patients by additional studies - among others : [PMID 31814314] Impaired Arginyl-tRNA synthetase activity was demonstrated in fibroblasts from 3 patients. Activity was normal in one additional individual compound heterozygous for a variant affecting initiation codon and a missense one. Western blot however demonstrated presence mainly of the short protein isoform. The authors suggest that this isoform possibly contributed to enzymatic activity. The long isoform which is needed for the MSC complex was only represented by a faint band in the Western Blot of the same individual. [PMID: 28905880] Using fibroblasts from an affected subject homozygous for a missense variant (NM_002887.3:c.5A>G / p.Asp2Gly) and controls, a 75% reduction of the long isoform was shown upon WB. The short isoform was present at similar levels. As the N-terminus (of the long isoform) mediates interaction with the MSC (and AIMP1), assembly of the latter was 99% reduced in patient fibroblasts. Proliferation of patient fibroblasts was significantly reduced when cultured in a medium with limited arginine, a finding which was thought to reflect inefficient protein synthesis. Mutations in other genes encoding for aminoacyl-tRNA synthetases (eg. AARS1, VARS1) or scaffolding proteins of the multisynthetase complex (eg. AIMP1 and AIMP2) lead to neurodevelopmental disorders with overlapping phenotype [most genes rated green in both the ID and epilepsy panel]. Sources: Literature |
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| Intellectual disability - microarray and sequencing v2.1135 | TRAPPC4 |
Konstantinos Varvagiannis gene: TRAPPC4 was added gene: TRAPPC4 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: TRAPPC4 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: TRAPPC4 were set to 31794024 Phenotypes for gene: TRAPPC4 were set to Feeding difficulties; Progressive microcephaly; Intellectual disability; Seizures; Spastic tetraparesis; Abnormality of the face; Scoliosis; Cortical visual impairment; Hearing impairment Penetrance for gene: TRAPPC4 were set to Complete Review for gene: TRAPPC4 was set to GREEN Added comment: Van Bergen et al. (2019 - PMID: 31794024) report on 7 affected individuals from 3 famillies (only 1 of which consanguineous), all homozygous for a TRAPPC4 splicing variant. Overlapping features included feeding difficulties, progressive microcephaly, severe to profound developmental disability (7/7 - DD also prior to the onset of seizures / regression also reported in 3), epilepsy (7/7 - onset in the first year), spastic quadriparesis. Other findings in some/few incl. scoliosis, cortical visual and hearing impairment. Some facial features were shared (eg. bitemporal narrowing, long philtrum, open mouth with thin tented upper lip, pointed chin, etc). Brain imaging demonstrated abnormalities in those performed (among others cerebral with/without cerebellar atrophy). Work-up prior to exome sequencing was normal (highly variable incl. metabolic testing, CMA, MECP2, CDKL5, mitochondrial depletion studies, etc). Exome of affected individuals (and parents +/- affected sibs in some families) revealed a homozygous TRAPPC4 splicing variant [NM_016146.5:c.454+3A>G / chr11:g.118890966A>G (hg19)]. Sanger sequencing confirmed variant in affecteds, heterozygosity in parents and compatible genotypes with disease status in sibs/other members. Families were of Caucasian/Turkish and French-Canadian ethnicities. SNP array to compare haplotypes between affecteds in 2 families did not reveal a shared haplotype (/founder effect) and the variant is present in gnomAD (68/281054 - no hmz) in many populations (European/Asian/African/Latino) [https://gnomad.broadinstitute.org/variant/11-118890966-A-G]. mRNA studies in fibroblasts from an affected individual confirmed the splicing defect (2 RT-PCR products corresponding to wt and a shorter due to skipping of exon 3, the latter further confirmed by Sanger sequencing. The shorter transcript is not present in controls). qPCR revealed that the normal transript in patient fibroblasts was present at 6% of the level observed in control fibroblasts (or 54% in the case of a heterozygote parent compared to controls). Western blot in patient fibroblasts, revealed presence of full-length protein in significantly reduced levels compared to fibroblasts from carrier parents or controls. There was no band using an antibody targeting the N-terminal region of the protein prior to exon 3, suggesting that NMD applies (skipping of ex3 is also predicted to lead to frameshift). TRAPPC4 encodes one of the core proteins of the TRAPP complex. Use of different accessory proteins leads to formation of 2 distinct complexes (TRAPPII / III). The complex has an important role in intracellular trafficking. Both TRAPPII & TRAPPIII have a function in the secretory pathway, while complex III has a role also in autophagy. Core proteins are important for the complex stability. The TRAPP complex serves as a GEF for Ypt/Rab GTPases [several refs in article]. Mutations in genes for other proteins of the complex lead to neurodevelopmental disorders with associated ID ('TRAPPopathies' used by the authors / TRAPPC12, C6B, C9 green in the current panel). Western blot suggested that levels of other TRAPP subunits (TRAPPC2 or C12) under denaturing conditions, although PAGE/size exclusion chromatography suggested that the levels of fully-assembled TRAPP complexes were lower in affected individuals. Studies in patient fibroblasts showed a secretory defect (between ER, Golgi and the plasma membrane) which was restored upon lentiviral transduction with wt TRAPPC4 construct. Basal and starvation-induced autophagy were also impaired in patient fibroblasts (increased LC3 marker and LC3-positive structures / impaired co-localization with lysosomes) partly due to defective autophagosome formation (/sealing). TRAPPC4 is the human orthologue of the yeast Trs23. In a yeast model of reduced Trs23 (due to temperature instability) the authors demonstrated impaired assembly of the TRAPP core. The yeast model recapitulated the autophagy as well as well as the secretory defect observed in patient fibroblasts. Sources: Literature |
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| Intellectual disability - microarray and sequencing v2.1135 | SLC5A6 |
Konstantinos Varvagiannis changed review comment from: SLC5A6 encodes the sodium dependent multivitamin transporter (SMVT), a transporter of biotin, pantothenate and lipoate. The transporter has a major role in vitamin uptake in the digestive system (among others is the sole transporter for intestinal uptake of biotin which is not synthesized and but must be obtained from exogenous sources) as well as transport across the blood-brain barrier (SMVT being responsible for 89% of biotin transport) [several refs provided by Subramanian et al and Byrne et al]. 4 affected individuals from 3 families have been reported. Subramanian et al (2017 - PMID: 27904971) et al reported on a girl with feeding difficulties and failure to thrive (requiring nasogastric tube placement), microcephaly, DD (at 15m developmental age corresponding to 6m with features suggestive of spastic cerebral palsy), occurrence of multiple infections, osteoporosis and pathologic bone fractures. MRIs suggested brain atrophy, thin CC and hypoplasia of the pons. Metabolic (AA, OA) investigations and array-CGH were normal. Whole exome sequencing revealed presence of a missense (Arg123Leu - RefSeq not provided) and a nonsense (Arg94Ter) SLC5A6 variant. Serum biotin was normal although - at the time - the child was on parenteral and G-T nutrition. Following administration of biotin, pantothenic acid and lipoic acid the child demonstrated among others improved motor and verbal skills, head growth and normalization of immunoglobulin levels. Transfection of mutants in human derived intestinal HuTu-80 cells and brain U87 cells was carried out and a 3H-biotin assay showed no induction in biotin uptake confirming impaired functionality of the transporter. While wt protein displayed normal expression/membrane localization, Arg94Ter was poorly expressed with ectopic localization (cytoplasm). Arg123Leu was retained predominantly intracellularly, probably in the ER as was further supported by colocalization with DsRed-ER. Evidence from the literature is provided that deficiencies of the specific vitamins explain the clinical features (DD, microcephaly, immunological defect, osteopenia, etc). Schwantje et al (2019 - PMID: 31392107) described a girl with severe feeding problems, vomiting with blood (suspected Mallory-Weiss syndrome), poor weight gain and delayed gross motor development. The child presented an episode of gastroenteritis associated with reduced consciousness, circulatory insufficiency and metabolic derangement (hypoglycemia, severe metabolic acidosis, hyperammonemia, mild lactate elevation, ketonuria). Investigations some months prior to the admission (?) were suggestive of a metabolic disorder due to elevated plasma C3-carnitine, C5-OH-carnitine and elevated urinary excretion of 3-OH-isovaleric acid (biotinidase deficiency was considered in the DD but enzymatic activity was only marginally decreased). Biotin supplementation was initiated. Trio-exome sequencing (at 3yrs) demonstrated compound heterozygosity for 2 frameshift variants [NM_021095.2:c.422_423del / p.(Val141Alafs*34) and c.1865_1866del]. Following this result, increase of biotin supplementation and introduction of pantothenic acid, GI symptoms (incl. chronic diarrhea) resolved and the child displayed improved appetite and growth, yet a stable motor delay. The authors cite previous studies of conditional ko mice, displaying intestinal mucosal abnormalities and growth defects (similar to the child's problems), prevented by biotin and pantothenic acid supplementation. Byrne et al (2019 - PMID: 31754459) reported on a sibling pair with severe motor/speech developmental regression following a plateau (at 12m and 14m), development of ataxia and dyskinetic movements (both), seizures (one). Feeding difficulties, reflux and failure to thrive required N-G/gastrostomy feeding while both presented GI hemorrhage (in the case of the older sib, lethal). Other features in the youngest sib included brain MRI abnormalities (cerebral/cerebellar atrophy, thin CC, etc) and IgG deficiency. Biochemical, single-gene testing and mtDNA sequencing were not diagnostic. Exome in one, revealed presence of a frameshift [c.422_423del as above] and a missense variant (Arg400Thr). Sanger sequencing confirmed variants in both sibs and heterozygosity in parents. HeLa cells transfected with empty vector, wt or mut expression constructs confirmed significantly decreased 3H-biotin uptake for mut constructs compared to wt (and similar to empty vector). Parenteral triple vitamin replacement at the age of ~7 years resulted in improved overall condition, regain of some milestones, attenuation of vomiting, and resolution of peripheral neuropathy. Seizure were well-controlled (as was the case before treatment) despite persistence of epileptiform discharges. Again the authors cite studies of conditional (intestine-specific) SLC5A6 ko mice, with those viable (~1/3) demonstrating growth retardation, decreased boned density and GI abnormalities (similar to affected individuals). The phenotype could be rescued by oversupplementation of biotin and pantothenic acid (PMIDs cited: 23104561, 29669219). [Please consider inclusion in other relevant panels eg. metabolic disorders] Sources: Literature; to: SLC5A6 encodes the sodium dependent multivitamin transporter (SMVT), a transporter of biotin, pantothenate and lipoate. The transporter has a major role in vitamin uptake in the digestive system (among others is the sole transporter for intestinal uptake of biotin which is not synthesized but must be obtained from exogenous sources) as well as transport across the blood-brain barrier (SMVT being responsible for 89% of biotin transport) [several refs provided by Subramanian et al and Byrne et al]. 4 affected individuals from 3 families have been reported. Subramanian et al (2017 - PMID: 27904971) et al reported on a girl with feeding difficulties and failure to thrive (requiring nasogastric tube placement), microcephaly, DD (at 15m developmental age corresponding to 6m with features suggestive of spastic cerebral palsy), occurrence of multiple infections, osteoporosis and pathologic bone fractures. MRIs suggested brain atrophy, thin CC and hypoplasia of the pons. Metabolic (AA, OA) investigations and array-CGH were normal. Whole exome sequencing revealed presence of a missense (Arg123Leu - RefSeq not provided) and a nonsense (Arg94Ter) SLC5A6 variant. Serum biotin was normal although - at the time - the child was on parenteral and G-T nutrition. Following administration of biotin, pantothenic acid and lipoic acid the child demonstrated among others improved motor and verbal skills, head growth and normalization of immunoglobulin levels. Transfection of mutants in human derived intestinal HuTu-80 cells and brain U87 cells was carried out and a 3H-biotin assay showed no induction in biotin uptake confirming impaired functionality of the transporter. While wt protein displayed normal expression/membrane localization, Arg94Ter was poorly expressed with ectopic localization (cytoplasm). Arg123Leu was retained predominantly intracellularly, probably in the ER as was further supported by colocalization with DsRed-ER. Evidence from the literature is provided that deficiencies of the specific vitamins explain the clinical features (DD, microcephaly, immunological defect, osteopenia, etc). Schwantje et al (2019 - PMID: 31392107) described a girl with severe feeding problems, vomiting with blood (suspected Mallory-Weiss syndrome), poor weight gain and delayed gross motor development. The child presented an episode of gastroenteritis associated with reduced consciousness, circulatory insufficiency and metabolic derangement (hypoglycemia, severe metabolic acidosis, hyperammonemia, mild lactate elevation, ketonuria). Investigations some months prior to the admission (?) were suggestive of a metabolic disorder due to elevated plasma C3-carnitine, C5-OH-carnitine and elevated urinary excretion of 3-OH-isovaleric acid (biotinidase deficiency was considered in the DD but enzymatic activity was only marginally decreased). Biotin supplementation was initiated. Trio-exome sequencing (at 3yrs) demonstrated compound heterozygosity for 2 frameshift variants [NM_021095.2:c.422_423del / p.(Val141Alafs*34) and c.1865_1866del]. Following this result, increase of biotin supplementation and introduction of pantothenic acid, GI symptoms (incl. chronic diarrhea) resolved and the child displayed improved appetite and growth, yet a stable motor delay. The authors cite previous studies of conditional ko mice, displaying intestinal mucosal abnormalities and growth defects (similar to the child's problems), prevented by biotin and pantothenic acid supplementation. Byrne et al (2019 - PMID: 31754459) reported on a sibling pair with severe motor/speech developmental regression following a plateau (at 12m and 14m), development of ataxia and dyskinetic movements (both), seizures (one). Feeding difficulties, reflux and failure to thrive required N-G/gastrostomy feeding while both presented GI hemorrhage (in the case of the older sib, lethal). Other features in the youngest sib included brain MRI abnormalities (cerebral/cerebellar atrophy, thin CC, etc) and IgG deficiency. Biochemical, single-gene testing and mtDNA sequencing were not diagnostic. Exome in one, revealed presence of a frameshift [c.422_423del as above] and a missense variant (Arg400Thr). Sanger sequencing confirmed variants in both sibs and heterozygosity in parents. HeLa cells transfected with empty vector, wt or mut expression constructs confirmed significantly decreased 3H-biotin uptake for mut constructs compared to wt (and similar to empty vector). Parenteral triple vitamin replacement at the age of ~7 years resulted in improved overall condition, regain of some milestones, attenuation of vomiting, and resolution of peripheral neuropathy. Seizure were well-controlled (as was the case before treatment) despite persistence of epileptiform discharges. Again the authors cite studies of conditional (intestine-specific) SLC5A6 ko mice, with those viable (~1/3) demonstrating growth retardation, decreased boned density and GI abnormalities (similar to affected individuals). The phenotype could be rescued by oversupplementation of biotin and pantothenic acid (PMIDs cited: 23104561, 29669219). [Please consider inclusion in other relevant panels eg. metabolic disorders] Sources: Literature |
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| Intellectual disability - microarray and sequencing v2.1135 | SLC5A6 |
Konstantinos Varvagiannis gene: SLC5A6 was added gene: SLC5A6 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: SLC5A6 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: SLC5A6 were set to 27904971; 31392107; 31754459; 23104561; 29669219 Phenotypes for gene: SLC5A6 were set to Feeding difficulties; Failure to thrive; Global developmental delay; Developmental regression; Intellectual disability; Seizures; Microcephaly; Cerebral atrophy; Abnormality of the corpus callosum; Vomiting; Chronic diarrhea; Gastrointestinal hemorrhage; Abnormal immunoglobulin level; Osteopenia; Abnormality of metabolism/homeostasis Penetrance for gene: SLC5A6 were set to Complete Review for gene: SLC5A6 was set to GREEN Added comment: SLC5A6 encodes the sodium dependent multivitamin transporter (SMVT), a transporter of biotin, pantothenate and lipoate. The transporter has a major role in vitamin uptake in the digestive system (among others is the sole transporter for intestinal uptake of biotin which is not synthesized and but must be obtained from exogenous sources) as well as transport across the blood-brain barrier (SMVT being responsible for 89% of biotin transport) [several refs provided by Subramanian et al and Byrne et al]. 4 affected individuals from 3 families have been reported. Subramanian et al (2017 - PMID: 27904971) et al reported on a girl with feeding difficulties and failure to thrive (requiring nasogastric tube placement), microcephaly, DD (at 15m developmental age corresponding to 6m with features suggestive of spastic cerebral palsy), occurrence of multiple infections, osteoporosis and pathologic bone fractures. MRIs suggested brain atrophy, thin CC and hypoplasia of the pons. Metabolic (AA, OA) investigations and array-CGH were normal. Whole exome sequencing revealed presence of a missense (Arg123Leu - RefSeq not provided) and a nonsense (Arg94Ter) SLC5A6 variant. Serum biotin was normal although - at the time - the child was on parenteral and G-T nutrition. Following administration of biotin, pantothenic acid and lipoic acid the child demonstrated among others improved motor and verbal skills, head growth and normalization of immunoglobulin levels. Transfection of mutants in human derived intestinal HuTu-80 cells and brain U87 cells was carried out and a 3H-biotin assay showed no induction in biotin uptake confirming impaired functionality of the transporter. While wt protein displayed normal expression/membrane localization, Arg94Ter was poorly expressed with ectopic localization (cytoplasm). Arg123Leu was retained predominantly intracellularly, probably in the ER as was further supported by colocalization with DsRed-ER. Evidence from the literature is provided that deficiencies of the specific vitamins explain the clinical features (DD, microcephaly, immunological defect, osteopenia, etc). Schwantje et al (2019 - PMID: 31392107) described a girl with severe feeding problems, vomiting with blood (suspected Mallory-Weiss syndrome), poor weight gain and delayed gross motor development. The child presented an episode of gastroenteritis associated with reduced consciousness, circulatory insufficiency and metabolic derangement (hypoglycemia, severe metabolic acidosis, hyperammonemia, mild lactate elevation, ketonuria). Investigations some months prior to the admission (?) were suggestive of a metabolic disorder due to elevated plasma C3-carnitine, C5-OH-carnitine and elevated urinary excretion of 3-OH-isovaleric acid (biotinidase deficiency was considered in the DD but enzymatic activity was only marginally decreased). Biotin supplementation was initiated. Trio-exome sequencing (at 3yrs) demonstrated compound heterozygosity for 2 frameshift variants [NM_021095.2:c.422_423del / p.(Val141Alafs*34) and c.1865_1866del]. Following this result, increase of biotin supplementation and introduction of pantothenic acid, GI symptoms (incl. chronic diarrhea) resolved and the child displayed improved appetite and growth, yet a stable motor delay. The authors cite previous studies of conditional ko mice, displaying intestinal mucosal abnormalities and growth defects (similar to the child's problems), prevented by biotin and pantothenic acid supplementation. Byrne et al (2019 - PMID: 31754459) reported on a sibling pair with severe motor/speech developmental regression following a plateau (at 12m and 14m), development of ataxia and dyskinetic movements (both), seizures (one). Feeding difficulties, reflux and failure to thrive required N-G/gastrostomy feeding while both presented GI hemorrhage (in the case of the older sib, lethal). Other features in the youngest sib included brain MRI abnormalities (cerebral/cerebellar atrophy, thin CC, etc) and IgG deficiency. Biochemical, single-gene testing and mtDNA sequencing were not diagnostic. Exome in one, revealed presence of a frameshift [c.422_423del as above] and a missense variant (Arg400Thr). Sanger sequencing confirmed variants in both sibs and heterozygosity in parents. HeLa cells transfected with empty vector, wt or mut expression constructs confirmed significantly decreased 3H-biotin uptake for mut constructs compared to wt (and similar to empty vector). Parenteral triple vitamin replacement at the age of ~7 years resulted in improved overall condition, regain of some milestones, attenuation of vomiting, and resolution of peripheral neuropathy. Seizure were well-controlled (as was the case before treatment) despite persistence of epileptiform discharges. Again the authors cite studies of conditional (intestine-specific) SLC5A6 ko mice, with those viable (~1/3) demonstrating growth retardation, decreased boned density and GI abnormalities (similar to affected individuals). The phenotype could be rescued by oversupplementation of biotin and pantothenic acid (PMIDs cited: 23104561, 29669219). [Please consider inclusion in other relevant panels eg. metabolic disorders] Sources: Literature |
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| Intellectual disability - microarray and sequencing v2.1134 | OXR1 |
Konstantinos Varvagiannis gene: OXR1 was added gene: OXR1 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: OXR1 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: OXR1 were set to https://doi.org/10.1016/j.ajhg.2019.11.002 Phenotypes for gene: OXR1 were set to Central hypotonia; Global developmental delay; Delayed speech and language development; Intellectual disability; Seizures; Abnormality of the cerebellum Penetrance for gene: OXR1 were set to Complete Review for gene: OXR1 was set to GREEN Added comment: Wang et al (2019 - https://doi.org/10.1016/j.ajhg.2019.11.002 ) report on 5 individuals (from 3 families) with biallelic OXR1 LoF variants. Common features included hypotonia (4/5), severe global DD (5/5) and speech delay (5/5), ID (5/5), epilepsy (5/5) with cerebellar dysplasia/atrophy (5/5) and in some scoliosis. All were investigated by exome sequencing and were found to harbor biallelic loss-of-function variants (2 splice-site, a stopgain and a frameshift one) either in homozygosity (2 consanguineous families) or in compound heterozygosity. In all cases parental segregation studies were compatible and in one family, an unaffected sib shown to be carrier. Althouhgh OXR1 has been shown to affect several processes (among others DNA lesions induced by oxidative stress in E.coli, neuronal maintenance, mitochondrial morphology and DNA maintenance, etc), its mechanism of action is still not well defined. There are 6 RefSeq transcripts, the longest (NM_018002.3) encoding 3 protein domains (LysM, GRAM, TLDc). The TLDc domain is encoded by all transcripts. Identified variants affected (probably all - fig1D) transcripts expressed in the CNS, namely NM_018002.3, NM_001198532.1, NM_181354.4. The 3 transcripts not expressed in the CNS are NM_001198533.1, NM_001198534.1 and NM_001198535.1. Western blot with 2 different antibodies which would bind upstream of the truncation site failed to detect presence of truncated proteins in 2 affected individuals from 2 families. The Drosophila homolog of OXR is mustard (mtd). The authors provide evidence that loss of mtd is lethal. This was however rescued by expression of an 80kb fly BAC clone covering mtd, or the fly mtd-RH isoform cDNA, or a short human OXR1 cDNA containing only the TLDc domain or a human NCOA7 cDNA. The latter is another human mtd homolog which also contains the TLDc domain. As a result the TLDc domain compensated sufficiently for loss of mtd. Flies that survived displayed bang sensitivity and climbing defects the former assay being suggestive of susceptibility to seizures and the latter of impaired neurological/muscular function. The authors provided evidence that mtd is broadly expressed in the fly CNS. RNAi mediated mtd knockdown specific to neurons (elav/nSyb-GAL4 expression of mtd RNAi) led to lethal eclosion defects for RNAis targeting most (18)/all(23) mtd isoforms. Lifespan was increased upon expression of human OXR1 cDNA. Neuronal loss and vacuolization was demonstrated and additional experiments in R7 photoreceptors showed presence of aberrant lysosomal structures (autolysosomes, autophagosomes and/or endolysosomes). Aberrant lysosomal structures were also observed in fibroblasts from affected individuals (accumulation of lysosomes and/or presence of highly aberrant compartments with content typical of lysosomal dysfunction). Overall the data presented suggest a critical role for OXR1 in lysosomal biology. Although previous reports suggested that OXR1 is involved in oxidative stress resistance, studies performed by the authors suggested that oxidative stress is probably not the driver of the mutant fly defects. Sources: Literature |
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| Intellectual disability - microarray and sequencing v2.1122 | TMX2 |
Konstantinos Varvagiannis edited their review of gene: TMX2: Added comment: A recent report by Vandervore, Schot et al. following the previous review (Am J Hum Genet. 2019 Nov 12 - PMID: 31735293), provides further evidence that biallelic TMX2 mutations cause malformations of cortical development, microcephaly, DD and ID and epilepsy. As a result this gene should probably be considered for inclusion in the ID/epilepsy panels with green rating. Overall, 14 affected subjects from 10 unrelated families are reported in the aforementioned study. The majority had severe DD/ID (failure to achieve milestones, absent speech/ambulation and signs of cerebral palsy) with few having a somewhat milder impairment. 12 (of the 14) presented with epilepsy (spasms, myoclonic seizures, focal seizures with/without generalization or generalized tonic-clonic seizures) with onset most often in early infancy. Upon brain MRI (in 12 individuals), 5 presented polymicrogyria, 2 others pachygyria, 4 with brain atrophy, etc. All individuals were found to harbor biallelic TMX2 mutations by exome sequencing while previous investigations in several had ruled out alternative causes (infections, metabolic or chromosomal anomalies). Missense variants, an in-frame deletion as well as pLoF (stopgain/frameshift) variants were reported. [NM_015959.3 used as ref below]. The effect of variants was supported by mRNA studies, eg. RT-qPCR/allele specific RT-qPCR. The latter proved reduced expression for a frameshift variant (c.391dup / p.Leu131Profs*6) most likely due to NMD. Total mRNA levels were also 23% lower in an individual compound htz for a missense variant and a stopgain one localized in the last exon (c.757C>T / p.Arg253*). As for the previously reported c.614G>A (p.Arg205Gln), affecting the last nucleotide of exon 6, total mRNA in skin fibroblasts from a homozygous individual was not significantly decreased. RNA-Seq however demonstrated the presence of 4 different transcripts (roughly 25% each), one representing the regular mRNA, one with intron 6 retention (also present at low levels in healthy individuals), one with loss of 11 nucleotides within exon 6 and a fourth one due to in-frame skipping of exon 6. *To the best of my understanding : Thioredoxin (TRX)-related transmembrane proteins (TMX) belong to the broader family of oxidoreductases of protein disulfide isomerase (PDI) having an important role in protein folding. Study of the data from the Allen Human Brain Atlas suggest relevant fetal expression also increasing during postnatal life. As RNA-seq was carried out for 2 individuals, GO analysis suggested that the most deregulated clusters of genes are implicated in post-translational protein modifications (as would be expected for PDIs), membranes and synapse while pathway analysis suggested that relevant categories were inhibited eg. nervous system development/function and cell growth/proliferation/survival. Upon transfection of HEK293T cells, exogenous TMX2 was shown to co-localize with calnexin (CNX) to the (ER) mitochondria-associated-membrane. Mass-spectrometry based analysis of co-immunoprecipitated proteins confirmed interaction with CNX but also other regulators of calcium homeostasis, mitochondrial membrane components and respiratory chain NADH dehydrogenase. Study of the mitochondrial activity of TMX2-deficient fibroblasts suggested reduced respiratory reserve capacity, compensated by increased glycolytic activity. TMX2 occurs in both reduced and oxidized monomeric form. It also forms (homo)dimers with the ratio of dimers/monomers increasing under conditions of oxidative stress. Variant TMX2 increased propensity to form dimers, thus mimicking increased oxidative state. This was observed under stress but also under native conditions. ---------; Changed rating: GREEN |
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| Intellectual disability - microarray and sequencing v2.1102 | DMXL2 |
Konstantinos Varvagiannis changed review comment from: This gene can be considered for upgrade to green rating (ID and epilepsy with >=4 relevant individuals/families/variants and >=2 studies, role of the protein, effect of variants in most cases demonstrated, phenotypic similarities with other disorders affecting autophagy, some evidence from animal models, etc). Rare heterozygous variants disrupting DMXL2 (intragenic losses/gains, SNVs, CNVs affecting also additional genes) have been reported in individuals with variable neurodevelopmental disorders (ASD and ID) or psychiatric phenotypes [Costain et al. 2019 - PMID: 30732576 - summarized in Table 1]. (Highly) variable expressivity and possibly incomplete penetrance were proposed in the respective study. As a result evidence for ID/seizures due to monoallelic variants appears to be relatively limited. DD, ID and (probably) epilepsy appear however to be features in several individuals with biallelic pathogenic variants as summarized in the studies below. OMIM recently added a relevant entry with the DMXL2-associated phenotypes being the following: - Epileptic encephalopathy, early infantile, 81; EIEE81 - 618663 (AD) [based on refs 2,3] - ?Deafness, autosomal dominant 71 - 617605 (AD) [DD/ID/seizures are not part of the phenotype] - ?Polyendocrine-polyneuropathy syndrome - 616113 (AR) [based on ref1] DMXL2 is not associated with any phenotype in G2P. In SysID it is listed as a candidate ID gene based on the report by Tata et al (ref1). This gene is included in some gene panels for ID. [1] Tata el al. (2014 - PMID: 25248098) reported on 3 sibs born to consanguineous Senegalese parents, presenting with a progressive endocrine and neurodevelopmental disorder. Features incl. incomplete puberty, central hypothyroidism, abnormal glucose regulation, moderate ID (3/3) and peripheral polyneuropathy. Seizures were not part of the phenotype. Linkage analysis suggested 2 candidate regions on chromosomes 13 and 15 with a LOD score of 2.5. High throughput sequencing of genes within these regions (~500) in an affected member and parent revealed a 15 bp in-frame deletion of DMXL2 (NM_015263.4:c.5827_5841del / p.Asp1943_Ser1947del). Sanger sequencing of other affected and unaffected members supported AR inheritance. RT-qPCR demonstrated that DMXL2 mRNA levels in blood lymphocytes were significantly lower in homozygous patients compared to heterozygous or wt family members or controls. The authors demonstrated that the encoded protein (rabconnectin-3a) is a synaptic protein (expressed in exocytosis vesicles) at the ends of axons of GnRH producing neurons. Neuron-specific deletion of one allele in mice resulted in delayed puberty and very low fertility. Adult mice had lower number of GnRH neurons in hypothalamus. siRNA-mediated downregulation of Dmxl2 expression in an insulin-secreting cell line resulted in only slight insulin secretion in response to augmenting concentrations of glucose, providing evidence of involvement of the protein in control of regulated insulin secretion. ----------- [2] Maddirevula et al. (2019 - PMID: 30237576) reported briefly on a 36 months old boy, born to consanguineous parents, homozygous for a frameshift DMXL2 variant [individual 17-3220 | NM_001174117.1:c.4349_4350insTTACATGA or p.(Glu1450Aspfs*23)]. Features included focal seizures (onset at the age of 3m) with subsequent global DD, absent eye contact, cerebral atrophy and macrocephaly. This individual was identified following re-evaluation of exome data in a database of ~1550 exomes specifically for homozygous variants that would have been classified earlier as LP/P if the respective gene had sufficient evidence for association with a disorder. The family was not reported to have other affected members. As the authors noted, the boy was not known to have the multi-endocrine abnormalities reported by Tata et al. There are no additional information provided (eg. on confirmation of variants, etc). ----------- [3] Esposito et al. (2019 - PMID: 31688942) report on 3 sibling pairs (all 3 families unrelated) with biallelic DMXL2 mutations and summarize previous evidence on the gene and the DMXL2-related phenotypes. All presented a highly similar phenotype of Ohtahara syndrome (seizures with onset in the first days of life, tonic/myoclonic/occasionaly focal, burst-suppression upon EEG), profound DD/ID, quadriparesis, sensorineural hearing loss and presence of dysmorphic features. Sibs from 2 families presented evidence of peripheral polyneuropathy. Early brain MRIs revealed thin CC and hypomyelination in all, with later scans suggestive of gray and white matter shrinkage with leukoencephalopathy. None achieved developmental skills following birth with 5/6 deceased by the age of 9 years. Exome sequencing revealed biallelic DMXL2 variants in all, with compatible parental segregation studies (NM_015263.3): - Fam1 (2 sibs) : c.5135C>T (p.Ala1712Val) in trans with c.4478C>G (p.Ser1493*) - Fam2 (2 sibs) : homozygosity for c.4478C>A (p.Ser1493*) - Fam3 (2 sibs) : homozygosity for c.7518-1G>A Heterozygous parents (aged 39-59) did not exhibit hearing impairment [report of a single multigenerational family by Chen et al (2017 - PMID: 27657680) where a heterozygous missense variant segregated with hearing loss - respective OMIM entry: ?Deafness, autosomal dominant 71 - 617605]. In patients' fibroblasts, effect of the variants on mRNA/protein expression was demonstrated with mRNA expressed only in a patient from family 1, and degraded/absent for the 2 stopgain SNVs affecting codon 1493. Skipping of ex31 leading to frameshift/introduction of a PTC was shown for the splice variant (p.Trp2508Argfs*4 secondary to c.7518-1G>A). Protein was also absent upon western-blot. DMXL2 encodes a vesicular protein, DmX-Like protein 2 or rabconnectin-3a (cited Tata et al). The gene is expressed in brain ( https://www.gtexportal.org/home/gene/DMXL2 ). As Esposito et al comment, it is known to regulate the trafficking and activity of v-ATPase the latter having a role in acidifying intracellular organelles and promoting endosomal maturation (cited PMIDs : 25248098, 19758563, 22875945, 24802872). In line with this, staining of patients' fibroblasts using the acidotropic dye LysoTracker demonstrated increased signal, reversed by re-expression of DMXL2 protein. Overall an acidic shift in pH with impairment of lysosomal structures and function was suggested. The authors provided additional evidence for altered lysosomal function and associated autophagy with accumulation of autophagy receptors (eg p62) and substrates (polyubiquitinated proteins). Vacuolization and accumulation of atypical fusion-like structures was shown upon ultrastractural analysis. shRNA-mediated downregulation/silencing of Dmxl2 in mouse hippocampal neurons resulted also in altered lysosomal structures and defective autophagy. The neurons exhibited impaired neurite elongation and synapse formation. The authors suggest similarities with Vici syndrome, where biallelic EPG5 mutations result in autophagic defects and clinical manifestations of DD/ID/epilepsy. Dmxl2 homozygous ko mice display embryonic lethality with heterozygous mice displaying macrocephaly and corpus callosum dysplasia (cited PMIDs: 25248098, 30735494) .; to: This gene can be considered for upgrade to green rating (ID and epilepsy with >=4 relevant individuals/families/variants and >=2 studies, role of the protein, effect of variants in most cases demonstrated, phenotypic similarities with other disorders affecting autophagy, some evidence from animal models, etc). Rare heterozygous variants disrupting DMXL2 (intragenic losses/gains, SNVs, CNVs affecting also additional genes) have been reported in individuals with variable neurodevelopmental disorders (ASD and ID) or psychiatric phenotypes [Costain et al. 2019 - PMID: 30732576 - summarized in Table 1]. (Highly) variable expressivity and possibly incomplete penetrance were proposed in the respective study. As a result evidence for ID/seizures due to monoallelic variants appears to be relatively limited. DD, ID and (probably) epilepsy appear however to be features in several individuals with biallelic pathogenic variants as summarized in the studies below. OMIM recently added a relevant entry with the DMXL2-associated phenotypes being the following: - Epileptic encephalopathy, early infantile, 81; EIEE81 - 618663 (AR) [based on refs 2,3] - ?Deafness, autosomal dominant 71 - 617605 (AD) [DD/ID/seizures are not part of the phenotype] - ?Polyendocrine-polyneuropathy syndrome - 616113 (AR) [based on ref1] DMXL2 is not associated with any phenotype in G2P. In SysID it is listed as a candidate ID gene based on the report by Tata et al (ref1). This gene is included in some gene panels for ID. [1] Tata el al. (2014 - PMID: 25248098) reported on 3 sibs born to consanguineous Senegalese parents, presenting with a progressive endocrine and neurodevelopmental disorder. Features incl. incomplete puberty, central hypothyroidism, abnormal glucose regulation, moderate ID (3/3) and peripheral polyneuropathy. Seizures were not part of the phenotype. Linkage analysis suggested 2 candidate regions on chromosomes 13 and 15 with a LOD score of 2.5. High throughput sequencing of genes within these regions (~500) in an affected member and parent revealed a 15 bp in-frame deletion of DMXL2 (NM_015263.4:c.5827_5841del / p.Asp1943_Ser1947del). Sanger sequencing of other affected and unaffected members supported AR inheritance. RT-qPCR demonstrated that DMXL2 mRNA levels in blood lymphocytes were significantly lower in homozygous patients compared to heterozygous or wt family members or controls. The authors demonstrated that the encoded protein (rabconnectin-3a) is a synaptic protein (expressed in exocytosis vesicles) at the ends of axons of GnRH producing neurons. Neuron-specific deletion of one allele in mice resulted in delayed puberty and very low fertility. Adult mice had lower number of GnRH neurons in hypothalamus. siRNA-mediated downregulation of Dmxl2 expression in an insulin-secreting cell line resulted in only slight insulin secretion in response to augmenting concentrations of glucose, providing evidence of involvement of the protein in control of regulated insulin secretion. ----------- [2] Maddirevula et al. (2019 - PMID: 30237576) reported briefly on a 36 months old boy, born to consanguineous parents, homozygous for a frameshift DMXL2 variant [individual 17-3220 | NM_001174117.1:c.4349_4350insTTACATGA or p.(Glu1450Aspfs*23)]. Features included focal seizures (onset at the age of 3m) with subsequent global DD, absent eye contact, cerebral atrophy and macrocephaly. This individual was identified following re-evaluation of exome data in a database of ~1550 exomes specifically for homozygous variants that would have been classified earlier as LP/P if the respective gene had sufficient evidence for association with a disorder. The family was not reported to have other affected members. As the authors noted, the boy was not known to have the multi-endocrine abnormalities reported by Tata et al. There are no additional information provided (eg. on confirmation of variants, etc). ----------- [3] Esposito et al. (2019 - PMID: 31688942) report on 3 sibling pairs (all 3 families unrelated) with biallelic DMXL2 mutations and summarize previous evidence on the gene and the DMXL2-related phenotypes. All presented a highly similar phenotype of Ohtahara syndrome (seizures with onset in the first days of life, tonic/myoclonic/occasionaly focal, burst-suppression upon EEG), profound DD/ID, quadriparesis, sensorineural hearing loss and presence of dysmorphic features. Sibs from 2 families presented evidence of peripheral polyneuropathy. Early brain MRIs revealed thin CC and hypomyelination in all, with later scans suggestive of gray and white matter shrinkage with leukoencephalopathy. None achieved developmental skills following birth with 5/6 deceased by the age of 9 years. Exome sequencing revealed biallelic DMXL2 variants in all, with compatible parental segregation studies (NM_015263.3): - Fam1 (2 sibs) : c.5135C>T (p.Ala1712Val) in trans with c.4478C>G (p.Ser1493*) - Fam2 (2 sibs) : homozygosity for c.4478C>A (p.Ser1493*) - Fam3 (2 sibs) : homozygosity for c.7518-1G>A Heterozygous parents (aged 39-59) did not exhibit hearing impairment [report of a single multigenerational family by Chen et al (2017 - PMID: 27657680) where a heterozygous missense variant segregated with hearing loss - respective OMIM entry: ?Deafness, autosomal dominant 71 - 617605]. In patients' fibroblasts, effect of the variants on mRNA/protein expression was demonstrated with mRNA expressed only in a patient from family 1, and degraded/absent for the 2 stopgain SNVs affecting codon 1493. Skipping of ex31 leading to frameshift/introduction of a PTC was shown for the splice variant (p.Trp2508Argfs*4 secondary to c.7518-1G>A). Protein was also absent upon western-blot. DMXL2 encodes a vesicular protein, DmX-Like protein 2 or rabconnectin-3a (cited Tata et al). The gene is expressed in brain ( https://www.gtexportal.org/home/gene/DMXL2 ). As Esposito et al comment, it is known to regulate the trafficking and activity of v-ATPase the latter having a role in acidifying intracellular organelles and promoting endosomal maturation (cited PMIDs : 25248098, 19758563, 22875945, 24802872). In line with this, staining of patients' fibroblasts using the acidotropic dye LysoTracker demonstrated increased signal, reversed by re-expression of DMXL2 protein. Overall an acidic shift in pH with impairment of lysosomal structures and function was suggested. The authors provided additional evidence for altered lysosomal function and associated autophagy with accumulation of autophagy receptors (eg p62) and substrates (polyubiquitinated proteins). Vacuolization and accumulation of atypical fusion-like structures was shown upon ultrastractural analysis. shRNA-mediated downregulation/silencing of Dmxl2 in mouse hippocampal neurons resulted also in altered lysosomal structures and defective autophagy. The neurons exhibited impaired neurite elongation and synapse formation. The authors suggest similarities with Vici syndrome, where biallelic EPG5 mutations result in autophagic defects and clinical manifestations of DD/ID/epilepsy. Dmxl2 homozygous ko mice display embryonic lethality with heterozygous mice displaying macrocephaly and corpus callosum dysplasia (cited PMIDs: 25248098, 30735494) . |
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| Intellectual disability - microarray and sequencing v2.1098 | PCYT2 |
Konstantinos Varvagiannis gene: PCYT2 was added gene: PCYT2 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: PCYT2 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: PCYT2 were set to 31637422 Phenotypes for gene: PCYT2 were set to Global developmental delay; Developmental regression; Intellectual disability; Spastic paraparesis; Seizures; Spastic tetraparesis; Cerebral atrophy; Cerebellar atrophy Penetrance for gene: PCYT2 were set to Complete Review for gene: PCYT2 was set to GREEN Added comment: Vaz et al. (2019 - PMID: 31637422 - DDD study among the co-authors) report on 5 individuals - from 4 families - with biallelic PCYT2 mutations. The phenotype corresponded to a complex hererditary paraplegia with global DD, regression (4/5), ID (mild in 3/5, severe in 2/5), spastic para-/tetraparesis, epilepsy (5/5 - variable onset 2-16 yrs - focal or tonic-clonic seizures) and progressive cerebral and cerebellar atrophy. Exome sequencing in all revealed biallelic PCYT2 variants, confirmed with Sanger s. in probands and their parents (NM_001184917.2 - corresponding to the canonical transcript used as Ref below): - P1 (Fam1) : 2 missense SNVs in trans configuration, c.730C>T or p.His244Tyr and c.920C>T or p.Pro307Leu - P2 (Fam2 - consanguineous of White British origin), P3 (Fam3 - Consanguineous of Turkish origin), P4,5 (Fam4 - consanguineous, unspecified origin) : homozygosity for c.1129C>T or p.Arg377Ter) affecting the last exon of 8/12 transcripts, including the canonical one. Individuals with the same genotype displayed variable degrees of ID (eg P3 - severe / P2, P4,5 - mild ID). For sibs in Fam4, homozygosity for a missense SACS variant led to consideration of the respective disorder (AR spastic ataxia of Charlevoix-Saguenay) though the variant was predicted to be tolerated in silico and notably the MRI images not suggestive. All variants were absent from / had extremely low AF in public databases, with no homozygotes. Posphatidylethanolamine (PE) is a membrane lipid, particularly enriched in human brain (45% of phospholypid fraction). PE is synthesized either via the CDP-ethanolamine pathway or by decarboxylation of phosphatidylserine in mitochondria. PCYT2 encodes CTP:phosophoethanolamine cytidyltransferase (ET) which is an ubiquitously expressed rate-limiting enzyme for PE biosynthesis in the former pathway. In silico, the 2 missense variants - localizing in the CTP catalytic domain 2 - were predicted to be damaging, as well as to affect protein stability. Fibroblasts of 3 patients (P1, P2, P3) representing all variants were studied: - Enzymatic activity was shown to be significantly reduced (though not absent) compared to controls. Abnormalities were noted upon Western Blot incl. absence in all 3 patients studied of one of the 2 bands normally found in controls (probably representing the longer isoform), reduced intensity in all 3 of another band probably corresponding to a shorter isoform, and presence of an additional band of intermediate molec. mass in patients with the truncating variant. - RT-PCR on mRNA from patient fibroblasts did not reveal (significant) reduction compared to controls. - Lipidomic profile of patient fibroblasts was compatible with the location of the block in the phospholipid biosynthesis pathway and different from controls. The lipidomic profile had similarities with what has been reported for EPT1 deficiency, the enzyme directly downstream of ET. The SELENO1-related phenotype (/EPT1 deficiency) is also highly overlapping. CRISPR-Cas9 was used to generate pcyt2 partial or complete knockout (ko) zebrafish, targeting either the final (ex13) or another exon (ex3) respectively. mRNA expression was shown to be moderately reduced in the first case and severely reduced/absent in the second, compared to wt. Similarly, complete-ko (ex3) led to significantly lower survival, with impaired though somewhat better survival of partial-ko (ex13) zebrafish. Complete knockout of Pcyt2 in mice is embryonically lethal (PMID cited: 17325045) while heterozygous mice develop features of metabolic syndrome (PMID cited: 22764088). Given lethality in knockout zebrafish / mice and the residual activity (15-20%) in patient fibroblasts, the variants reported were thought to be hypomorphic and complete loss of function possibly incompatible with life. PCYT2 is not associated with any phenotype in OMIM/G2P/SysID and not commonly included in gene panels for ID. As a result this gene could included in the ID / epilepsy panels with green (~/>3 indiv/fam/variants with the nonsense found in different populations, consistent phenotype, lipidomics, in silico/in vitro/in vivo evidence) or amber rating. [Please consider inclusion in other possibly relevant panels eg. for metabolic disorders, etc]. Sources: Literature |
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| Intellectual disability - microarray and sequencing v2.1062 | TDP2 |
Konstantinos Varvagiannis gene: TDP2 was added gene: TDP2 was added to Intellectual disability. Sources: Literature,Radboud University Medical Center, Nijmegen Mode of inheritance for gene: TDP2 was set to MONOALLELIC, autosomal or pseudoautosomal, NOT imprinted Publications for gene: TDP2 were set to 24658003; 30109272; 31410782 Phenotypes for gene: TDP2 were set to Spinocerebellar ataxia, autosomal recessive 23, 616949) Penetrance for gene: TDP2 were set to unknown Review for gene: TDP2 was set to GREEN gene: TDP2 was marked as current diagnostic Added comment: Biallelic pathogenic TGP2 variants cause Spinocerebellar ataxia, autosomal recessive 23 (MIM 616949). At least 6 affected individuals from 4 families have been reported, in all cases homozygous for LoF variants (3 different). ID, epilepsy and ataxia are consistent features of the disorder. TDP2 encodes a phosphodiesterase that is required for efficient repair of double strand breaks (DSBs) produced by abortive topoisomerase II (TOP2) activity. The gene is expressed in fetal and adult human brain. Evidence at the variant level (mRNA, protein levels) and additional studies for impairment of TOP2-induced DSB repair support a role. Animal models (primarily mice) reproduce the DSB repair defect, provide some histopathological evidence, show transcriptional dysregulation of genes (in line with the role of TOP2 in transcription). They have however failed to reproduce relevant neurological phenotypes. Published studies are summarized below. TDP2 is included in gene panels for ID offered by some diagnostic laboratories (incl. Radboudumc and GeneDx). There is no associated phenotype in G2P. TDP2 is listed among the current primary ID genes in SysID. Overall, this gene could be considered for inclusion in the ID and epilepsy panels probably as green (>=3 patients/families/variants, relevant ID and seizures in all, expression in brain, mRNA/protein levels tested, impaired activity) or amber (absence of neurological phenotypes in mouse model). ------------ [1] - PMID: 24658003 (Gómez-Herreros et al. 2014): Reports 3 individuals from a consanguineous Irish family. Features included seizures (onset by 2m, 6m and 12y), ID (3/3) and ataxia (3/3). A splicing variant (NM_016614.3:c.425+1G>A) was found in a 9.08-Mb region of homozygosity shared by all. A further ZNF193 missense variant localizing in the same region was thought unlikely to contribute to the phenotype (evidence also provided in subsequent study). The effect of the specific variant was proven by abnormal mRNA size, lower mRNA levels due to NMD (corrected upon cyclohexamide treatment), loss of TDP2 protein upon WB, loss of protein activity in lymphoblastoid cells from affected individuals, decreased repair of DSBs and increased cell death upon addition of etoposide (which promotes TOP2 abortive activity). The authors report very briefly on a further patient (from Egypt), with ID, 'reports of fits' and ataxia. This individual, with also affected sibs, was homozygous LoF (c.413_414delinsAA / p.Ser138*). Again, the authors were not able to detect TDP2 activity in blood from this subject. As also commented: - TDP2 has relevant expression in human (particularly adult) brain. - Mouse model : Tdp2 is expressed in relevant tissues, absence of Tdp2 activity was observed in neural tissue of mice homoyzgous for an ex1-3 del, with impairment of DSB repair. The authors were unable to detect a neurological phenotype with behavioral analyses, preliminary assesment of seizure propensity. Mice did not show developmental defects. Histopathology however, revealed ~25% reduction in the density of interneurons in cerebellum (a 'hallmark of DSB repair' and associated with seizures and ataxia). Transcription of several genes was shown to be disregulated. - Knockdown in zebrafish appears to affect left-right axis detremination (cited PMID: 18039968). [2] - PMID: 30109272 (Zagnoli-Vieira et al. 2018): A 6 y.o. male with seizures (onset by 5m), hypotonia, DD and ID, microcephaly and some additional clinical features and testing (ETC studies on muscle biopsy, +lactate, +(lactate/pyruvate) ratio) which could be suggestive of mitochondrial disorder. This individual from the US was homozygous for the c.425+1G>A variant but lacked the ZNF193 one (despite a shared haplotype with the Irish patients). Again absence of the protein was shown upon WB in patient fibroblasts, also supported by its activity. Complementation studies restored the DSB repair defect. The defect was specific to TOP2-induced DSBs as suggested by hypersensitivity to etoposide but not to ionizing radiation. CRISPR/Cas9 generated mutant human A549 cells demonstrated abnormal DSB repair. Fibroblasts / edited A549 cells failed to show mitochondrial defects (which were noted in muscle). [3] - PMID: 31410782 (Ciaccio et al. 2019): A girl born to consanguineous Italian parents, presented with moderate/severe ID, seizures (onset at 12y) and - among others - gait ataxia, tremor and dysmetria. MRI at the age of 12, demonstrated cerebellar atrophy (although previous exams were N). WES revealed a homozygous nonsense variant (c.400C>T / p.Arg134Ter) for which each parent was found to be carrier. Previous investigations included aCGH, NGS testing for epilepsy and metabolic testing. Sources: Literature, Radboud University Medical Center, Nijmegen |
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| Intellectual disability - microarray and sequencing v2.1059 | PIGU | Rebecca Foulger Phenotypes for gene: PIGU were changed from Global developmental delay; Intellectual disability; Seizures; Cerebral atrophy; Cerebellar hypoplasia; Scoliosis to Glycosylphosphatidylinositol biosynthesis defect 2, 618590; Global developmental delay; Intellectual disability; Seizures; Cerebral atrophy; Cerebellar hypoplasia; Scoliosis | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v2.1051 | KCNMA1 | Catherine Snow Phenotypes for gene: KCNMA1 were changed from GENERALIZED EPILEPSY AND PAROXYSMAL DYSKINESIA to Cerebellar atrophy, developmental delay, and seizures, 617643; Paroxysmal nonkinesigenic dyskinesia, 3, with or without generalized epilepsy, 609446 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v2.1047 | KCNMA1 | Catherine Snow reviewed gene: KCNMA1: Rating: AMBER; Mode of pathogenicity: None; Publications: 31427379, 31152168; Phenotypes: Cerebellar atrophy, developmental delay, and seizures, 617643; Mode of inheritance: BOTH monoallelic and biallelic, autosomal or pseudoautosomal | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v2.1047 | CSDE1 |
Konstantinos Varvagiannis gene: CSDE1 was added gene: CSDE1 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: CSDE1 was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: CSDE1 were set to http://doi.org/10.1126/sciadv.aax2166 Phenotypes for gene: CSDE1 were set to Autism; Global developmental delay; Intellectual disability Penetrance for gene: CSDE1 were set to unknown Review for gene: CSDE1 was set to GREEN Added comment: Guo et al. (2019 - DOI: 10.1126/sciadv.aax2166) report on 18 individuals from 18 unrelated families, with heterozygous likely gene disrupting (stopgain/frameshift/spice-site) CSDE1 variants. Initial sequencing with MIPs found in 3 individuals from an autism cohort (4045 probands), while subsequent targeted sequencing of a larger cohort (autism spectrum/ID network) led to identification of 5 additional relevant individuals and Genematcher/collaborations a further 10 (the latter by WES). Consistent phenotypes included ASD (10 of 15 formally evaluated), DD (motor: 15/17 - speech: 17/17) and ID (mild to severe in 14 of 16 assessed, in further 2 in the below-average range). Recurrent seizures or epilepsy were reported for 7 of 16 patients. Other variable features were anxiety or ADHD, increased OFC, ocular, hand and MRI anomalies. The study was mainly focused on LGD variants with p.R123* (NM_001242891.1:c.367C>T) being a reccurrent one, found in 3 families. 8 of these variants were de novo, 8 further inherited (often from a less severely affected parent, although parental neuropsychiatric status was not available for individuals from all 3 groups). In 2 cases inheritance was unknown (only 1 parental sample available). 3 individuals with de novo missense variants were also identified. Features in those individuals also included ASD and/or DD and ID (2/3) [Table S1]. Arguments to support involvement of the CSDE1 variants included the: - role of the gene encoding an RNA binding protein implicated in neuronal migration/differentiation (cited : 24012837, 29129916), - statistically significant burden of the variants in the cohorts examined, - relevant CSDE1 intolerance scores (pLI of 1 and %RVIS of 6.18), - relevant human (mRNA) / mouse (protein) spatial and temporal expression patterns, - exclusion of apparent alternative diagnoses to the extent possible in many subjects with CNVs/SNVs/ROH of uncertain significance in very few, - cosegregation with rather similar neuropsychiatric phenotypes in case of carrier parents, - enrichment of ASD-related genes (and FMRP targets) among CSDE1-binding targets, - suppression of Ctnnb1 expression (at the protein level) affecting Wnt/β-catenin signalling, - effect of knockdown and/or mutants in mouse (shRNA) and Drosophila (mt and siRNA) models affecting synapse formation and synaptic transmission, - rescue of many of the previous phenotypes by expression of human CSDE1 (mice), expression of stabilized β-Catenin (mice) or RNAi-stable-dUNR (Drosophila) [also supporting LoF as the underlying effect of variants]. CSDE1 is not commonly included in gene panels for ID offered by diagnostic laboratories. There is no associated phenotype in OMIM/G2P. Overall, this gene could be considered for inclusion in the ID panel probably as green (or amber). Sources: Literature |
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| Intellectual disability - microarray and sequencing v2.1046 | PMPCB |
Konstantinos Varvagiannis changed review comment from: Biallelic pathogenic PMPCB variants cause, Multiple mitochondrial dysfunctions syndrome 6 (MIM 617954). 5 relevant individuals from 4 unrelated families (in one case consanguineous) have been reported by Vögtle et al. (2018 - PMID: 29576218). Onset of symptoms (eg. hypotonia) often preceded a period of developmental regression/stagnation which was common in all individuals and occurred within the first 2 years of life, usually following febrile illness. In all cases neurological features were severe (lack of ambulation/speech). Seizures were observed in 4 individuals from 3 families, with onset at the age of 11-24m. MRI images demonstrated T2 signal hyperintensities of the basal ganglia with cerebellar and cerebral atrophy in some. Deterioration with early death was reported on three occasions, though some years after symptom onset. Following exclusion of other diagnoses in some cases (eg. aCGH, epilepsy panel), WES identified biallelic PMPCB missense variants, supported by Sanger confirmation and segregation studies. The following variants were reported (NM_004279.2): - c.523C>T (p.Arg175Cys) in trans with c.601G>C (p.Ala201Pro) [Fam A and B] - c.524G>A (p.Arg175His) in trans with c.530T>G (p.Val177Gly) [Fam C] - c.1265T>C (p.Ile422Thr) in homozygous state [Fam D with 2 affected sibs] The gene encodes the catalytic (beta) subunit of the mitochondrial processing protease (MPP) which is responsible for the cleavage/maturation of nuclear-encoded mitochondrial precursor proteins after their import in mitochondria. The alpha subunit is encoded by PMPCA (green rating proposed for this panel). Extensive studies demonstrated (perhaps a better summary provided by OMIM): - Reduced PMPCB protein levels in mitochondria isolated from patient fibroblasts or patient-derived pluripotent stem cells. - Frataxin maturation was impaired with accumulation of the intermediate form and lower amounts of mature FXN, indicating decrease in MPP activity. - Analysis of the homologous Mas1 S. cerevisiae mutants was carried out, with the exception of Ile422Thr (corresponding to Mas1 - Ile398Thr), the introduction of which did not yield viable yiest strains. Homologous mutations led to a temperature-sensitive phenotype with accumulation of immature/unprocessed precursor proteins and decrease of mature/processed forms both in vivo or in organello (following isolation of mitochondria). Under conditions of heat stress, Mas1 mutations decreased biogenesis of Fe-S clusters. - Respiratory chain complexes I-III contain Fe-S clusters. In muscle biopsy from an affected individual, complex II activity was significantly reduced (although this was not the case in fibroblasts or liver biopsy). Dysfunction of mitochondrial and cytosolic Fe-S cluster-dependent enzymes (eg. aconitase) was also shown in muscle tissue. Regression/stagnation with seizures/non-achievement of milestones may justify testing for an ID / epilepsy gene panel. In addition, metabolic studies or mitochondrial respiratory chain complex studies were sometimes non-informative (lactate elevated in 3/5 subjects) or not carried out at all / in relevant tissues (muscle biopsy in 2 individuals, fibroblasts/liver biopsy did not demonstrate reduced complex activity when tested). PMPCB is included in the ID gene panel of Radboudumc, as well as the SysID database. The gene is included in the DD panel of G2P associated with "Neurodegeneration in Early Childhood" (disease confidence : probable). As a result, PMPCB can be considered for inclusion in both epilepsy and ID panels as green (or amber). Sources: Literature, Radboud University Medical Center, Nijmegen; to: Biallelic pathogenic PMPCB variants cause, Multiple mitochondrial dysfunctions syndrome 6 (MIM 617954). 5 relevant individuals from 4 unrelated families (in one case consanguineous) have been reported by Vögtle et al. (2018 - PMID: 29576218). Onset of symptoms (eg. hypotonia) often preceded a period of developmental regression/stagnation which was common in all individuals and occurred within the first 2 years of life, usually following febrile illness. In all cases neurological features were severe (lack of ambulation/speech). Seizures were observed in 4 individuals from 3 families, with onset at the age of 11-24m. MRI images demonstrated T2 signal hyperintensities of the basal ganglia with cerebellar and cerebral atrophy in some. Deterioration with early death was reported on three occasions, though some years after symptom onset. Following exclusion of other diagnoses in some cases (eg. aCGH, epilepsy panel), WES identified biallelic PMPCB missense variants, supported by Sanger confirmation and segregation studies. The following variants were reported (NM_004279.2): - c.523C>T (p.Arg175Cys) in trans with c.601G>C (p.Ala201Pro) [Fam A and B] - c.524G>A (p.Arg175His) in trans with c.530T>G (p.Val177Gly) [Fam C] - c.1265T>C (p.Ile422Thr) in homozygous state [Fam D with 2 affected sibs] The gene encodes the catalytic (beta) subunit of the mitochondrial processing protease (MPP) which is responsible for the cleavage/maturation of nuclear-encoded mitochondrial precursor proteins after their import in mitochondria. The alpha subunit is encoded by PMPCA (green rating proposed for this panel). Extensive studies demonstrated (perhaps a better summary provided by OMIM): - Reduced PMPCB protein levels in mitochondria isolated from patient fibroblasts or patient-derived pluripotent stem cells. - Frataxin maturation was impaired with accumulation of the intermediate form and lower amounts of mature FXN, indicating decrease in MPP activity. - Analysis of the homologous Mas1 S. cerevisiae mutants was carried out, with the exception of Ile422Thr (corresponding to Mas1 - Ile398Thr), the introduction of which did not yield viable yeast strains. Homologous mutations led to a temperature-sensitive phenotype with accumulation of immature/unprocessed precursor proteins and decrease of mature/processed forms both in vivo or in organello (following isolation of mitochondria). Under conditions of heat stress, Mas1 mutations decreased biogenesis of Fe-S clusters. - Respiratory chain complexes I-III contain Fe-S clusters. In muscle biopsy from an affected individual, complex II activity was significantly reduced (although this was not the case in fibroblasts or liver biopsy). Dysfunction of mitochondrial and cytosolic Fe-S cluster-dependent enzymes (eg. aconitase) was also shown in muscle tissue. Regression/stagnation with seizures/non-achievement of milestones may justify testing for an ID / epilepsy gene panel. In addition, metabolic studies or mitochondrial respiratory chain complex studies were sometimes non-informative (lactate elevated in 3/5 subjects) or not carried out at all / in relevant tissues (muscle biopsy in 2 individuals, fibroblasts/liver biopsy did not demonstrate reduced complex activity when tested). PMPCB is included in the ID gene panel of Radboudumc, as well as the SysID database. The gene is included in the DD panel of G2P associated with "Neurodegeneration in Early Childhood" (disease confidence : probable). As a result, PMPCB can be considered for inclusion in both epilepsy and ID panels as green (or amber). Sources: Literature, Radboud University Medical Center, Nijmegen |
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| Intellectual disability - microarray and sequencing v2.1046 | PMPCB |
Konstantinos Varvagiannis gene: PMPCB was added gene: PMPCB was added to Intellectual disability. Sources: Literature,Radboud University Medical Center, Nijmegen Mode of inheritance for gene: PMPCB was set to BIALLELIC, autosomal or pseudoautosomal Phenotypes for gene: PMPCB were set to Multiple mitochondrial dysfunctions syndrome 6, 617954 Penetrance for gene: PMPCB were set to Complete Review for gene: PMPCB was set to GREEN gene: PMPCB was marked as current diagnostic Added comment: Biallelic pathogenic PMPCB variants cause, Multiple mitochondrial dysfunctions syndrome 6 (MIM 617954). 5 relevant individuals from 4 unrelated families (in one case consanguineous) have been reported by Vögtle et al. (2018 - PMID: 29576218). Onset of symptoms (eg. hypotonia) often preceded a period of developmental regression/stagnation which was common in all individuals and occurred within the first 2 years of life, usually following febrile illness. In all cases neurological features were severe (lack of ambulation/speech). Seizures were observed in 4 individuals from 3 families, with onset at the age of 11-24m. MRI images demonstrated T2 signal hyperintensities of the basal ganglia with cerebellar and cerebral atrophy in some. Deterioration with early death was reported on three occasions, though some years after symptom onset. Following exclusion of other diagnoses in some cases (eg. aCGH, epilepsy panel), WES identified biallelic PMPCB missense variants, supported by Sanger confirmation and segregation studies. The following variants were reported (NM_004279.2): - c.523C>T (p.Arg175Cys) in trans with c.601G>C (p.Ala201Pro) [Fam A and B] - c.524G>A (p.Arg175His) in trans with c.530T>G (p.Val177Gly) [Fam C] - c.1265T>C (p.Ile422Thr) in homozygous state [Fam D with 2 affected sibs] The gene encodes the catalytic (beta) subunit of the mitochondrial processing protease (MPP) which is responsible for the cleavage/maturation of nuclear-encoded mitochondrial precursor proteins after their import in mitochondria. The alpha subunit is encoded by PMPCA (green rating proposed for this panel). Extensive studies demonstrated (perhaps a better summary provided by OMIM): - Reduced PMPCB protein levels in mitochondria isolated from patient fibroblasts or patient-derived pluripotent stem cells. - Frataxin maturation was impaired with accumulation of the intermediate form and lower amounts of mature FXN, indicating decrease in MPP activity. - Analysis of the homologous Mas1 S. cerevisiae mutants was carried out, with the exception of Ile422Thr (corresponding to Mas1 - Ile398Thr), the introduction of which did not yield viable yiest strains. Homologous mutations led to a temperature-sensitive phenotype with accumulation of immature/unprocessed precursor proteins and decrease of mature/processed forms both in vivo or in organello (following isolation of mitochondria). Under conditions of heat stress, Mas1 mutations decreased biogenesis of Fe-S clusters. - Respiratory chain complexes I-III contain Fe-S clusters. In muscle biopsy from an affected individual, complex II activity was significantly reduced (although this was not the case in fibroblasts or liver biopsy). Dysfunction of mitochondrial and cytosolic Fe-S cluster-dependent enzymes (eg. aconitase) was also shown in muscle tissue. Regression/stagnation with seizures/non-achievement of milestones may justify testing for an ID / epilepsy gene panel. In addition, metabolic studies or mitochondrial respiratory chain complex studies were sometimes non-informative (lactate elevated in 3/5 subjects) or not carried out at all / in relevant tissues (muscle biopsy in 2 individuals, fibroblasts/liver biopsy did not demonstrate reduced complex activity when tested). PMPCB is included in the ID gene panel of Radboudumc, as well as the SysID database. The gene is included in the DD panel of G2P associated with "Neurodegeneration in Early Childhood" (disease confidence : probable). As a result, PMPCB can be considered for inclusion in both epilepsy and ID panels as green (or amber). Sources: Literature, Radboud University Medical Center, Nijmegen |
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| Intellectual disability - microarray and sequencing v2.1046 | PMPCA |
Konstantinos Varvagiannis gene: PMPCA was added gene: PMPCA was added to Intellectual disability. Sources: Literature,Radboud University Medical Center, Nijmegen Mode of inheritance for gene: PMPCA was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: PMPCA were set to 25808372; 26657514; 27148589; 30617178 Phenotypes for gene: PMPCA were set to Spinocerebellar ataxia, autosomal recessive 2 (MIM 213200) Penetrance for gene: PMPCA were set to Complete Review for gene: PMPCA was set to GREEN gene: PMPCA was marked as current diagnostic Added comment: Biallelic pathogenic PMPCA variants cause Spinocerebellar ataxia, autosomal recessive 2 (SCAR2 - MIM 213200). More than 20 individuals from several unrelated families have been reported. At least 6 different pathogenic variants have been identified. Loss of PMPCA function is the suggested mechanism. ID is a feature of the disorder. PMPCA encodes the α-subunit of mitochondrial processing peptidase (αMPP), a heterodimeric enzyme responsible for the cleavage of nuclear-encoded mitochondrial precursor proteins after import in the mitochondria (summary by Jobling et al and OMIM). Arguments for involvement of the gene include the highly similar phenotype, segregation studies, expression of the gene in fetal and relevant adult tissues (in brain/cerebellum/cerebellar vermis), lower protein levels demonstrated for some variants, abnormal processing of frataxin (in line with the role of αMPP) demonstrated in most cases, rescue of the maturation defect upon transduction of wt PMPCA cDNA, disruption of REDOX balance in patient cells, etc. Relevant studies are summarized below. PMPCA is included in gene panels for ID offered by several diagnostic laboratories (incl. Radboud UMC, GeneDx, etc) and listed as a confirmed ID gene in SysID. It is not associated with any phenotype in G2P. As a result, this gene can be considered for inclusion in the current panel probably as green (or amber). ---- [1] - Jobling et al. (2015 - PMID: 25808372) described the phenotype of 17 individuals from 4 families, all presenting with non-progressive cerebellar ataxia and the majority with ID of variable severity (15/17 - relevant to the current panel). Individuals from 3 of the families - all of Lebanese origin - were homozygous for NM_015160.3:c.1129G>A (p.Ala377Thr). A further similarly affected subject was compound heterozygous for c.287C>T (p.Ser96Leu) and c.1543G>A (p.Gly515Arg). The homozygous variant in the first family was found within a 2.85 Mb linkage region on chr 9q34. An additional variant within this region (in CAMSAP1) was discarded following results in other families of the same origin. Semi-quantitative RT-PCR demonstrated fetal expression of the PMPCA as well as relatively higher expression in adult brain, cerebellum and cerebellar vermis. As for Ala377Thr, protein levels were shown to be lowest in affected individuals (LCLs, fibroblasts) and low - though somewhat higher - in carrier parents (LCL) compared to controls. RT-PCR on total RNA from LCLs did not show evidence of abnormal transcripts/additional splicing defect. Localization of mutant protein and morphology of mitochondrial reticulum was similar to controls. Maturation of frataxin - the protein depleted in Friedreich ataxia - was shown to be abnormal in patient lymphoblasts, compatible with the role of αMPP. In line with abnormal mitochondrial function, REDOX balance was increased in patient cells. [2] - Choquet et al. (2016 - PMID: 26657514) reported on 2 sibs - born to distantly related parents. The authors noted a phenotype corresponding to SCAR2 although the presentation was somewhat milder, intellectual disability was not a feature (despite some learning difficulties in one) and ataxia was progressive. WES demonstrated homozygosity for NM_015160:c.766G>A (p.Val256Met). Western blot in patient lymphoblasts showed αMPP levels similar to carriers and controls. Abnormal maturation (accumulation of specific isoforms) was shown for frataxin. [3] - Joshi et al. (2016 - PMID: 27148589) described the phenotype of 2 cousins belonging to a large Lebanese pedigree. Presentation in both was compatible with multisystem involvement incl. profound global DD, severe hypotonia, weakness, respiratory insufficiency, blindness suggestive of mitochondrial disorder. mtDNA, analyses of mitochondrial focused nuclear gene panel and aCGH were non-diagnostic. Both subjects were compound heterozygous for NM_015160.3:c.1066G>A (p.Gly356Ser) and c.1129G>A (p.Ala377Thr) following WES, with compatible segregation studies within the family. Western blot revealed PMPCA levels similar to control. Reduction of PMPCA staining and abnormally enlarged mitochondria were observed upon immunofluorescence in patient fibroblasts. Frataxin processing was abnormal. Lentiviral transduction of patient fibroblasts with wt PMPCA cDNA, led to increased PMPCA levels and correction of frataxin processing. [4] - Rubegni et al. (2019 - PMID: 30617178) report on a 7-y.o. boy with global DD, spastic-ataxic gait and 'low IQ'. MRI images were suggestive of cerebellar atrophy with hyperintensity in the striatum. The child was homozygous for c.553C>T / p.Arg185Trp (reference not specified, although the variant would be compatible with NM_015160.3). Sources: Literature, Radboud University Medical Center, Nijmegen |
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| Intellectual disability - microarray and sequencing v2.1038 | CACNA2D2 | Rebecca Foulger Phenotypes for gene: CACNA2D2 were changed from Cerebellar atrophy with seizures and variable developmental delay (MIM 618501) to Cerebellar atrophy with seizures and variable developmental delay, 618501 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v2.1022 | CACNA2D2 |
Konstantinos Varvagiannis gene: CACNA2D2 was added gene: CACNA2D2 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: CACNA2D2 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: CACNA2D2 were set to 23339110; 24358150; 30410802; 29997391; 31402629; 11487633; 11756448; 4177347; 14660671; 15331424 Phenotypes for gene: CACNA2D2 were set to Cerebellar atrophy with seizures and variable developmental delay (MIM 618501) Penetrance for gene: CACNA2D2 were set to Complete Review for gene: CACNA2D2 was set to AMBER gene: CACNA2D2 was marked as current diagnostic Added comment: Gene reviewed for the epilepsy panel. Due to the phenotype of EE, with variable GDD (severe in many cases) and/or ID (either specifically commented on or inferred in some cases, although not universal) this gene might also be relevant for the current panel. CACNA2D2 is also included in gene panels for ID offered by some diagnostic laboratories (eg. GeneDx) as well as the SysID database. There is no associated phenotype in G2P. Copied from the epilepsy panel: Biallelic pathogenic CACNA2D2 variants cause Cerebellar atrophy with seizures and variable developmental delay (MIM 618501). A recent OMIM update, a subsequent relevant publication by Punatha et al. as well as several additional LP/P variants in ClinVar for the phenotype of epileptic encephalopathy, support possible upgrade to green. The following affected individuals appear to be relevant [NM_006030.3 used as RefSeq unless otherwise specified]: [1] Edvardson et al. (PMID: 23339110) - 3 sibs born to consanguineous parents with EIEE, severe GDD / ID (inferred from the descritpion, at least for the oldest one), cerebellar atrophy and movement abnormalities. A CACNA2D2 variant (c.3137T>C / p.Leu1046Pro) was found in affected individuals by SNP-arrays and WES in one of them. Functional studies (reduction in current density of calcium channels in Xenopus laevis oocytes) supported the deleterious effect of the variant. A role of a rare hmz CESLR3 variant could not be ruled out. [2] Pippucci et al. (PMID: 24358150) - 1 individual born to consanguineous parents, presenting with EE (onset at 1-2 m), severe GDD, cerebellar atrophy and choreiform movements. Homozygosity for a LoF variant (c.1294delA - p.Asn432fs) was found by WES. The role of the variant was further supported by expression studies (80% reduced mRNA levels, protein levels estimated at 3% of control / milder effect in htz parents). The proband was also hmz for a CESLR3 variant. Previous studies incl. 'high-resolution karyotype' and metabolic investigations. [3] Butler et al. (PMID: 30410802) - A 5 y.o. male, with EE (seizure onset at 7m / GDD) and cerebellar atrophy. Compound heterozygosity for c.782C>T (p.Pro261Leu) and c.3137T>C (p.Leu1046Pro) was demonstrated by WES and supported by segregation studies. [4] Valence et al. (PMID: 29997391) - Reported on a 20 y.o. male belonging to a cohort of 20 individuals with congenital ataxia, all from consaguineous families. This individual, who had cerebellar atrophy, ataxia, a single episode of febrile seizures and normal cognitive impairment was homozygosity for c.2971G>A (p.Asp991Asn). RT-PCR revealed presence of a normal length transcript as well as an additional, longer one, due to a concurrent splicing effect (activation of a cryptic donor splice site and retention of 4 bases of intronic sequence). Presence of both nl/abn length transcripts was presumed to explain the mild phenotype (variability also commented in OMIM). [5] Punatha et al. (PMID: 31402629) - 3 affected individuals from 2 consanguineous families presenting with early onset EE (onset 1-7m), GDD/ID, cerebelar atrophy and ataxia. Sibs from the first family were homozygous for c.1778G>C (p.Arg593Pro). An affected 5 y.o. child from the 2nd family was homozygous for c.485_486delAT (p.Tyr162Ter). Mutations were found by WES in regions of AOH. The following variants - not reported in the literature - have been submitted in ClinVar as LP / P for EE: [VCV000645106.1] NM_006030.4:c.1389+2T>C - EIEE with suppression bursts - Likely Pathogenic (Invitae) [VCV000570589.1] NM_006030.4:c.1956_1960del (p.Asn652fs) - EIEE - Pathogenic (Invitae) [VCV000578284.1] NM_006030.4:c.1555C>T (p.Gln519Ter) - EIEE - Pathogenic (Invitae) [VCV000653393.1] NM_006030.4:c.851dup (p.Ala286fs) - EIEE with suppression bursts - Pathogenic (Invitae) [VCV000411003.1] NM_006030.4:c.485_486del (p.Tyr161_Tyr162insTer) - EIEE - Pathogenic (Invitae) Additional ones have been reported as LP / P although the condition is not specified. [VCV000620551.1] NM_006030.4:c.1023C>A (p.Cys341Ter) - Likely pathogenic (GeneDx) [VCV000373439.2] NM_006030.4:c.1846-1G>A - Likely pathogenic (GeneDx) [VCV000423330.2] NM_006030.4:c.200dup (p.His68fs) - Pathogenic (GeneDx). The aforementioned laboratories include CACNA2D2 in gene panels for epilepsy (Invitae) and/or ID (GeneDx). A role for the CACNA2D2 is supported by : - The highly overlapping features (with the exception of the milder phenotype reported by Valence et al.) incl. early onset of seizures, GDD, cerebellar atrophy in all (9/9 incl. the individual reported by Valence, as evaluated Punatha et al). Ataxia was a feature in many (with movement abnormalities also in the remaining ones). - The role of the gene encoding the alpha-2-delta-2 auxiliary subunit of high voltage-gated calcium channels. Auxiliary subunits modulate calcium current and channel activation and inactivation kinetics, and may be involved in proper assembly and membrane localization of the channels (summary by Edvardson and OMIM). - Functional / expression studies for some of the variants (as in Refs 1,2,4). - Relevant expression patterns (notably in cerebellum) [GTEx project] - Mouse models recapitulating the human phenotypes (summarized by Edvardson et al) : The 'ducky' mouse model (due to biallelic Cacna2d2 mutations) presenting absence epilepsy, spike-wave seizures and ataxia. Dysgenesis of the cerebellum is among the neuropathological findings (PMIDs cited : 11487633, 11756448, 4177347). The 'entla' mouse model (also AR due to an in-frame duplication) presents also epilepsy and ataxia (PMID : 14660671). Targeted knockout in another mouse model resulted also in ataxic gait, seizure susceptibility and cerebellar anomalies/degeneration (PMID: 15331424). [Please consider inclusion in other relevant panels eg. for cerebellar anomalies / ataxia]. Sources: Literature |
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| Intellectual disability - microarray and sequencing v2.1022 | QARS | Louise Daugherty edited their review of gene: QARS: Added comment: Added new-gene-name tag, new approved HGNC gene symbol for QARS is QARS1; Changed publications: 28620870, 24656866, 25041233, 25471517, 25432320, 24709618; Changed phenotypes: Microcephaly, progressive, seizures, and cerebral and cerebellar atrophy, 615760, Intellectual disability | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v2.1015 | GOT2 |
Konstantinos Varvagiannis gene: GOT2 was added gene: GOT2 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: GOT2 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: GOT2 were set to 31422819 Phenotypes for gene: GOT2 were set to Global developmental delay; Intellectual disability; Seizures; Increased serum lactate; Hyperammonemia; Microcephaly; Failure to thrive; Feeding difficulties; Abnormality of nervous system morphology Penetrance for gene: GOT2 were set to Complete Review for gene: GOT2 was set to GREEN Added comment: van Karnebeek et al. (2019 - PMID: 31422819) report on 4 individuals from 3 families, with biallelic GOT2 pathogenic variants (3 missense SNVs and 1 in-frame deletion). The phenotype corresponded to a metabolic encephalopathy with onset of epilepsy in the first year of life (4/4) with DD and ID (4/4). Additional features included postnatal microcephaly, failure to thrive/feeding difficulties and cerebral anomalies (atrophy and white matter). All subjects had high blood lactate and hyperammonemia. Plasma serine was low in one case (alternative causes were ruled out). Administration of serine and pyridoxine led to clinical improvement (cessation / better control of seizures) in 2 subjects suggesting that GOT2 deficiency may be amenable to therapeutic intervention. [Treatment could not be started in the 2 further affected individuals]. GOT2 encodes the mitochondrial glutamate oxaloacetate transaminase, a component of the malate-aspartate shuttle (MAS). The latter is important for intracellular NAD(H) redox homeostasis. The authors provide several lines of evidence that GOT2 deficiency explains the patients' phenotype and metabolic defects incl. : - Reduced GOT2 protein levels (due to lower expression/impaired stability) and diminished activity in patient fibroblasts (lower activity was also shown for carriers). Rescue of the GOT enzymatic activity was observed upon transduction of patient fibroblasts using lentiviral particles with wt GOT2. - Impairment of de novo serine biosynthesis in patient (and to a lesser extent in carrier) fibroblasts compared to controls. This was similar in GOT2-knockout HEK293 cells. Serine biosynthesis in these cells was restored by pyruvate supplementation. - CRISPR/Cas9 Got2-knockout mice resulted in early lethality (during pregnancy). Heterozygous mice were viable and healthy. - Morpholino knockdown of got2a in zebrafish was shown to perturb embryonic development (smaller head, slow circulation, bend body, brain developmental defects, etc). Pyridoxine and serine in embryo water resulted in milder phenotypes/improved morphant survival. Zebrafish got2a morphants had seizure-like spikes upon EEG that were rescued by treatment with pyridoxine. GOT2 is not associated with any phenotype in OMIM/G2P. As a result, this gene can be considered for inclusion in both epilepsy and ID gene panels probably as green (3 families, relevant phenotypes and severity, evidence from cell and animal studies) or amber. [Please consider inclusion in other relevant panels eg. mitochondrial disorders, metabolic disorders and/or addition of the 'treatable' tag]. Sources: Literature |
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| Intellectual disability - microarray and sequencing v2.996 | PIGU |
Konstantinos Varvagiannis gene: PIGU was added gene: PIGU was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: PIGU was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: PIGU were set to 31353022 Phenotypes for gene: PIGU were set to Global developmental delay; Intellectual disability; Seizures; Cerebral atrophy; Cerebellar hypoplasia; Scoliosis Penetrance for gene: PIGU were set to Complete Review for gene: PIGU was set to GREEN Added comment: Knaus et al. (2019 - PMID: 31353022) report on 5 affected individuals (from 3 unrelated families) with biallelic pathogenic PIGU variants. Common features included tone abnormalities, global DD, ID, seizures, CNS anomalies (cerebral atrophy and/or cerebellar hypoplasia), scoliosis. Affected individuals presented also with facial similarities. DD/ID were universal features and their severity appears to be relevant to the panel. Seizures were also reported in all individuals (myoclonic in 3, for whom this was specified). ALP was normal in all. Three individuals from 2 non-consanguineous families (one from Norway, the other not specified) were homozygous for a missense variant NM_080476.4:c.1149C>A (or p.Asn383Lys) present with an AF of 7/277197 in Europeans. Two individuals born to consanguineous parents from Turkey were homozygous for another missense variant (c.209T>A or p.Ile70Lys - same RefSeq). Segregation analyses in parents and unaffected sibs were carried out. PIGU encodes a subunit of the GPI transaminidase, a heteropentameric complex (other subunits encoded by PIGK, PIGS, PIGT and GPAA1) that mediates attachment in the endoplasmic reticulum of glycosylphosphatidylinositol (GPI) to the C-termini of proteins which are subsequently anchored to the cell surface. Pathogenic variants in 18 of 29 genes implicated in biosynthesis of the GPI anchor have been identified as a cause of GPI biosynthesis disorders, with ID and seizures as principal features. Mutations in other genes encoding components of the GPI transaminidase complex (GPAA1, PIGT and PIGS) lead to neurodevelopmental disorders. Functional impairment of PIGU was supported by flow-cytometric analysis showing significant reduction of cell surface expression of GPI anchored proteins (mainly FLAER, CD16 and CD24) on granulocytes from affected individuals. In addition accumulation of free GPI anchors on the cell surface of B cells from affected individuals further suggested deficiency of the GPI transaminidase. Transient expression of mutant (Asn383Lys) protein failed to rescue expression of GPI-APs to the same extent as wt in a CHO cell line deficient for PIGU. Feature analysis demonstrated similarities among individuals with mutations in other genes of the GPI transamidase complex (GPAA1 and PIGT) as well as with GPI biosynthesis disorders. Facial analysis was also suggestive of facial similarities between individuals with GPAA1 and PIGU mutations. PIGU is not associated with any phenotype in OMIM or G2P. As a result this gene can be considered for inclusion in the ID and epilepsy panels probably as green (3 families, ID of relevant severity and seizures in all affected individuals, known group of disorders and supportive evidence) or amber. Sources: Literature |
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| Intellectual disability - microarray and sequencing v2.978 | VARS |
Catherine Snow Source Expert Review Green was added to VARS. Added phenotypes Neurodevelopmental disorder with microcephaly, seizures, and cortical atrophy, 617802 for gene: VARS Publications for gene VARS were changed from 26539891; 29691655; 30275004 to 26539891; 30275004; 29691655 Rating Changed from No List (delete) to Green List (high evidence) |
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| Intellectual disability - microarray and sequencing v2.978 | EMC1 |
Catherine Snow Source Expert Review Green was added to EMC1. Added phenotypes Cerebellar atrophy, visual impairment, and psychomotor retardation, 616875 for gene: EMC1 Publications for gene EMC1 were changed from 26942288; 29271071 to 29271071; 26942288; 30914295 Rating Changed from No List (delete) to Green List (high evidence) |
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| Intellectual disability - microarray and sequencing v2.965 | ATN1 | Catherine Snow Phenotypes for gene: ATN1 were changed from Dentatorubro-pallidoluysian atrophy 125370 to Generalized hypotonia; Global developmental delay; Intellectual disability; Seizures; Feeding difficulties; Abnormality of the cardiovascular system; Cleft palate; Abnormality of the kidney | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v2.959 | ATRX | Rebecca Foulger Added comment: Comment on mode of inheritance: Changed Mode of inheritance from XLR to XLD: Alpha-thalassemia/mental retardation syndrome, 301040 is listed as XLD in OMIM (in addition to Mental retardation-hypotonic facies syndrome, X-linked, 309580 listed as XLR). Although PMID:17503331 report that nearly all female carriers of ATRX syndrome have highly skewed X-chromosome inactivation in favour of cells expressing the normal ATRX allele and are essentially phenotypically normal, PMID:16955409 report a female carrier where the chromosome carrying the mutant allele was active and she therefore showed a phenotype. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v2.959 | ATRX | Rebecca Foulger Mode of inheritance for gene: ATRX was changed from X-LINKED: hemizygous mutation in males, biallelic mutations in females to X-LINKED: hemizygous mutation in males, monoallelic mutations in females may cause disease (may be less severe, later onset than males) | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v2.958 | ATRX | Rebecca Foulger Publications for gene: ATRX were set to 25529582; 24896178; 26860117; 26997013; 10995512; 7697714; 12116232; 15565397; 8644709; 9244431; 9598720 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v2.957 | ATRX | Rebecca Foulger commented on gene: ATRX: PMID:16955409: Badens et al. 2006 report a 4 year old female with a heterozygous R246C variant in ATRX and a skewed pattern of X-inactivation where her maternally-inherited X chromosome that carried the de novo variant remained active. Clinical features included severed DD. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v2.957 | ATRX | Rebecca Foulger commented on gene: ATRX | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v2.957 | ATRX | Rebecca Foulger Phenotypes for gene: ATRX were changed from Alpha-thalassemia/mental retardation syndrome, 301040Alpha-thalassemia myelodysplasia syndrome, somatic, 300448Mental retardation-hypotonic facies syndrome, X-linked, 309580; MENTAL RETARDATION SYNDROMIC X-LINKED WITH HYPOTONIC FACIES SYNDROME TYPE 1 (MRXSHF1) to Alpha-thalassemia/mental retardation syndrome, 301040; Mental retardation-hypotonic facies syndrome, X-linked, 309580 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v2.956 | ATRX | Rebecca Foulger Publications for gene: ATRX were set to | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v2.953 | DEGS1 |
Konstantinos Varvagiannis gene: DEGS1 was added gene: DEGS1 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: DEGS1 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: DEGS1 were set to 30620337; 30620338; 31186544 Phenotypes for gene: DEGS1 were set to Leukodystrophy hypomyelinating 18, MIM 618404) Penetrance for gene: DEGS1 were set to Complete Review for gene: DEGS1 was set to GREEN Added comment: Several individuals with biallelic pathogenic DEGS1 variants have been reported to date, in the following studies : [1] Pant et al. 2019 (PMID: 30620337) : 19 patients from 13 unrelated families [2] Karsai et al. 2019 (PMID: 30620338) : 1 individual [3] Dolgin et al. 2019 (PMID: 31186544) : 4 individuals belonging to a large consanguineous kindred As summarized in the first article and OMIM, affected individuals may have very poor psychomotor development, dystonia, spasticity, seizures with hypomyelinating leukodystrophy upon brain imaging and/or progressive atrophy of corpus callosum, thalami and cerebellum. Although a severe form overall was reported for many individuals in the first study, variable severity (eg. mild to severe ID) was reported among individuals belonging to the same kindred in the report by Dolgin et al. DEGS1 encodes Δ4-dehydroceramide desaturase which catalyzes conversion of dihydroceramide (DhCer) to ceramide (Cer) in the de novo ceramide biosynthetic pathway. Ceramide is the central unit of all sphingolipids, which are components of cellular membranes and play key roles in several processes incl. cell differentiation, neuronal signaling and myelin sheath formation. Sphingolipid balance is important for the CNS as demonstrated in the case of lysosomal disorders (eg. Gaucher, Niemann Pick, Farber) one enzymatic step away from DEGS1. Variants of all types (missense, stopgain, frameshift) have been reported with the majority/almost all located in the fatty acid desaturase (FAD) domain. Extensive studies have been carried out and demonstrated: - impaired DEGS1 activity in patients' fibroblasts and muscle suggested by increased DhCer/Cer ratio and compatible broader biochemical effects (higher levels of dihydrosphingosine, dihydrosphingomyelins, etc. and lower levels of sphingosine, monohexosylceramides, etc). - increased ROS production in patient fibroblasts (similar to a Drosophila model of excess DhCer), - high expression of the gene in child and adult CNS tissues from control individuals (evaluated by RT-qPCR in Ref. 1). A previous study has suggested that DEGS1 expression is upregulated during the 4-9th week of human embryogenesis (PMID cited: 20430792) which may suggest an important role for neural system development. - decreased expression for some variants either evaluated at the mRNA (RT-qPCR) / protein level (by Western Blot) - In zebrafish loss of Degs1 resulted in increased DhCer/Cer ratio, locomotor disability and impaired myelination similar to the patients' phenotype. Fingolimod, a sphingosine analog inhibiting Cer synthase (one step prior to DEGS1 in the de novo ceramide biosynthesis pathway, and converting sphingosine to ceramide in the salvage pathway) reduced the DhCer/Cer imbalance, ameliorated the locomotor phenotype and increased the number of myelinating oligodendrocytes in zebrafish, while it reduced the ROS levels in patient fibroblasts. Previous animal models: Apart from the zebrafish model (Pant et al.), higher DhCer/Cer ratios have been shown in homozygous Degs1 -/- mice similar to what is also observed in D. melanogaster. As summarized in MGI (and the previous studies as well) "mice homozygous for a knock-out allele exhibit premature death, decreased to absent ceramide levels, decreased body weight, scaly skin, sparse hair, tremors, hematological and blood chemistry abnormalities, decreased bone mineral content and density and decreased liver function." (PMIDs cited: 17339025, 28507162). ---- The respective OMIM entry is Leukodystrophy, hypomyelinating, 18 (#618404). DEGS1 is not associated with any phenotype in G2P. ---- As a result, DEGS1 can be considered for inclusion in the ID and epilepsy panels probably as green (relevant phenotype, sufficient number of individuals, supportive expression and biochemical studies, animal models, etc). Sources: Literature |
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| Intellectual disability - microarray and sequencing v2.923 | TRAPPC12 | Louise Daugherty Phenotypes for gene: TRAPPC12 were changed from Encephalopathy, progressive, early-onset, with brain atrophy and spasticity, 617669 to Encephalopathy, progressive, early-onset, with brain atrophy and spasticity, 617669; Developmental delay | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v2.922 | TRAPPC12 | Louise Daugherty Phenotypes for gene: TRAPPC12 were changed from to Encephalopathy, progressive, early-onset, with brain atrophy and spasticity, 617669 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v2.920 | TRAPPC12 | Louise Daugherty reviewed gene: TRAPPC12: Rating: GREEN; Mode of pathogenicity: None; Publications: 28777934; Phenotypes: Encephalopathy, progressive, early-onset, with brain atrophy and spasticity, 617669; Mode of inheritance: BIALLELIC, autosomal or pseudoautosomal | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v2.868 | PUF60 | Leanne Baxter reviewed gene: PUF60: Rating: ; Mode of pathogenicity: None; Publications: ; Phenotypes: Syndromic intellectual disability, prenatal onset growth failure, bifid uvula, retinal atrophy, congenital microcephaly, short stature, long fingers, deviation of toes, short thorax; Mode of inheritance: None | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v2.783 | TRRAP |
Konstantinos Varvagiannis gene: TRRAP was added gene: TRRAP was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: TRRAP was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: TRRAP were set to 30827496 Phenotypes for gene: TRRAP were set to Global developmental delay; Intellectual disability; Autism; Microcephaly; Abnormal heart morphology; Abnormality of the urinary system; Seizures Penetrance for gene: TRRAP were set to unknown Mode of pathogenicity for gene: TRRAP was set to Loss-of-function variants (as defined in pop up message) DO NOT cause this phenotype - please provide details in the comments Review for gene: TRRAP was set to GREEN gene: TRRAP was marked as current diagnostic Added comment: Cogné et al. (DDD study among the co-authors - PMID: 30827496) report on 24 individuals with pathogenic TRRAP variants. 17 different variants were reported. All variants were missense SNVs and on most occasions had occurred as de novo or apparently de novo events (paternity and maternity not checked). On one occasion, a parent was not unavailable although the respective grand-parents were not found to harbor the variant. Parental germline mosaicism explained the occurence of a variant in 2 sibs. The authors suggest a strong genotype-phenotype correlation. Individuals whose variant localized within the residues 1031-1159 (NM_001244580.1) presented with a syndromic form of ID with additional malformations. ID was a universal feature in this group (for those subjects evaluated). For variants outside this cluster of residues the phenotype was rather that of ASD without ID or isolated ID with or without ASD, albeit with some exceptions (eg. F860L also associated with a syndromic presentation). ID was a feature in the majority of individuals belonging to the latter group (67% - all with DD) or overall irrespective of the variant localization (85% for those evaluated - all with DD). Epilepsy was a feature in 4 individuals (4/24) belonging to either group. All 17 variants were absent from gnomAD with CADD scores supporting a deleterious effect (SIFT/PolyPhen2 (both) predicted a tolerated/benign effect for some eg. Ala1043Thr). A few variants were recurrent, namely Ala1043Thr (5 individuals), Glu1106Lys (2), Gly1883Arg (2), Pro1932Leu (in 2 sibs). 6 further subjects (individuals 25-30, reported separately in the supplement) harbored 6 additional variants with lesser evidence for pathogenicity. TRRAP is among the 5 most intolerant genes to missense mutations (z-score of 10.1 in ExAC) while it is also intolerant to LoF variants (pLI of 1). No deletions have been reported in DECIPHER and no LoF were identified in the study. Given type of variants and their clustering rather a gain-of-function effect or dominant-negative effect is suggested. As the authors note a LoF effect of non-clustering variants, associated with a milder phenotype cannot excluded. [Mode of pathogenicity to change if thought to be useful]. TRRAP encodes a protein involved in the recruitment to chromatin of histone acetyltransferases. The latter control the process of acetylation of lysine residues in histones and other DNA-binding proteins thus playing a major role in regulation of gene expression. In line with this, RNA sequencing analysis in skin fibroblasts from affected subjects demonstrated dysregulation of expression for several genes implicated in neuronal function and ion transport. As summarized by the authors: In mice, Trapp knockout is embryonically lethal. Brain-specific knockout leads to premature differentiation of neural progenitors and abnormal brain development. Brain atrophy and microcephaly are observed (microcephaly was a feature in some affected individuals as well, primarily those with variants affecting residues 1031-1159). [PMIDs cited: 11544477, 24792116]. De novo TRRAP variants have been reported also in individuals with neuropsychiatric disorders (PMIDs: 21822266, 23042115, 28392909, 30424743) while TRRAP has been classified among the prenatally-biased genes relevant to its brain expression (PMID:23042115). A de novo missense variant (c.11270G>A or p.R3757Q) was also previously reported in a study of 264 individuals with epileptic encephalopathy (Epi4K Consortium - PMID: 23934111 - indiv. ND29352). ----------- TRRAP is not associated with any phenotype in OMIM, nor in G2P. The gene is included in gene panels for ID offered by some diagnostic laboratories (eg. GeneDx participating in the current study). ----------- As a result, this gene can be considered for inclusion in the ID panel as green (or amber). Sources: Literature |
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| Intellectual disability - microarray and sequencing v2.705 | ASNS | Louise Daugherty Phenotypes for gene: ASNS were changed from Asparagine synthetase deficiency, 615574; congenital microcephaly, severe developmental delay, and axial hypotonia followed by spastic quadriplegia to Asparagine synthetase deficiency, 615574; congenital microcephaly, intellectual disability, progressive cerebral atrophy, intractable seizures | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v2.597 | PLEKHG2 |
Konstantinos Varvagiannis gene: PLEKHG2 was added gene: PLEKHG2 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: PLEKHG2 was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for gene: PLEKHG2 were set to 26539891; 26573021; 24001768 Phenotypes for gene: PLEKHG2 were set to Leukodystrophy and acquired microcephaly with or without dystonia, 616763 Penetrance for gene: PLEKHG2 were set to unknown Review for gene: PLEKHG2 was set to AMBER gene: PLEKHG2 was marked as current diagnostic Added comment: Karaca et al. (2015 - PMID: 26539891) in a study of 128 - mostly consanguineous - families with neurogenetic disorders and brain malformations, identified an individual homozygous for a PLEKHG2 missense variant (NM_022835.2:c.1708G>A or p.Gly570Arg). This individual (BAB4830) had a similarly affected sib. Features included hypotonia, intellectual disability, microcephaly, cerebellar atrophy and nystagmus (description provided in supplement - Table S1). This variant has been submitted in ClinVar as likely pathogenic by the corresponding laboratory (SCV000537940.1). ------- Edvardson et al. (2016 - PMID: 26573021) reported on 5 individuals from 2 unrelated consanguineous Palestinian families, harboring a missense variant in the homozygous state (NM_022835.2:c.610C>T or p.Arg204Trp - 1/5 was unavailable for testing). Unaffected relatives here either heterozygous for this variant or homozygous for the reference allele. Common features included hypotonia (5/5), DD/ID (5/5), postnatal microcephaly (5/5), dystonia (3/5), nystagmus (2/5) or seizures (1/5) [many of these similar to those reported by Karaca et al]. Brain MRI images were consistent with leukodystrophy and prolonged relaxation of dorsal tegmental tracts (similar findings were not commented by Karaca et al). PLEKHG2 encodes a Rho guanine exchange factor (RhoGEF). RhoGEFs activate RhoGTPases through release of GDP and binding of GTP. Mutations in other RhoGEFs have been associated with neurodevelopmental disorders. PLEKHG2 activity was shown to be significantly decreased in HEK293A cells transfected with R204W-PLEKHG2 when compared to tranfection with wt. Western blotting suggested that this was not the result of defective expression. Using lymphoblastoid cell lines from peripheral B lymphocytes from individuals homozygous for R204W and controls, similar levels of expression were shown between the 2 groups. As the authors note, PLEKHG2 is required for Rac- and Cdc42-stimulated actin polymerization in leukocytes (PMID cited: 24001768). SDF1a-stimulated actin polymerization was studied in patient cells and was shown to be significantly impaired. In line with this actin polymerization was also impaired upon siRNA-mediated downregulation of PLEKHG2 expression in control cells. ------- A subsequent submission of the Gly570Arg variant in ClinVar (2017 - SCV000609979.1 - same variant as the one reported by Karaca et al) reports this as a VUS. ------- PLEKHG2 is associated with Leukodystrophy and acquired microcephaly with or without dystonia (616763) in OMIM. This gene is not associated with any phenotype in G2P. PLEKHG2 is included in gene panels for ID offered by some diagnostic laboratories. ------- As a result, this gene could be considered for inclusion in this panel probably as amber (or green if the current evidence is considered to be sufficient). Sources: Literature |
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| Intellectual disability - microarray and sequencing v2.588 | MAPK8IP3 |
Konstantinos Varvagiannis gene: MAPK8IP3 was added gene: MAPK8IP3 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: MAPK8IP3 was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Phenotypes for gene: MAPK8IP3 were set to 25363768; 28213671; 28135719 Penetrance for gene: MAPK8IP3 were set to unknown Review for gene: MAPK8IP3 was set to GREEN Added comment: Platzer et al. (doi.org/10.1016/j.ajhg.2018.12.008) report on 13 unrelated individuals with de novo pathogenic variants in MAPK8IP3. The phenotype consisted - among others - of DD with ID (13/13) as well as variable brain anomalies (incl. cerebral or cerebellar atrophy, corpus callosum anomalies, perisylvian polymicrogyria, etc). Microcephaly, seizures, ataxia, ASD were features seen in fewer individuals. The variants reported included 2 nonsense, 1 frameshift as well as 6 missense mutations (3 missense variants were found - each - in 2 or more individuals). All three LoF variants were located in the first exon. (mRNA levels were not studied for these variants although NMD is presumed). The brain anomalies were more consistent for missense variants. MAPK8IP3 appears intolerant to LoF variants (pLI of 1) with constraint also for missense variants (Z-score of 4.06). In silico structural modeling was possible for 4 missense variants based on available crystal structures and different mechanisms were presumed (disruption of contacts between Leu444 of adjacent subunits, altered interaction between proximal residues at positions 461 and 466, or disruption of protein protein interactions). The C.elegans MAPK8IP3 ortholog is encoded by the unc-16 gene. Impaired clearance and accumulation of organelles (incl. lysosomes) in axons is observed in unc-16 mutants (recessive phenotype). For 6 variants, also conserved in C.elegans, mutants were engineered using CRISPR genome editing. The observed mutant phenotypes (increased axonal lysosomal density compared to controls for 2 variants, sluggish locomotion with lower swimming cycle rate for 1 nonsense and 4 missense variants) were rescued upon CRISPR reverse engineering of each mutant allele back to its wild-type sequence. The authors cite 3 previous studies, in which individuals investigated for neurodevelopmental disorders where found to harbor de novo MAPK8IP3 variants, namely: - PMID 25363768 (Iossifov et al.) : p.Tyr94Cys [ASD without ID] - PMID 28213671 (Berger et al.) : p.Glu461Gly [Smith-Magenis-like phenotype) - PMID 28135719 (DDD study) p.Arg1146Cys [This variant was found in 3 individuals in the study by Platzer et al.] ------------ A few additional individuals with neurodevelopmental disorders appear in the denovo-db after filtering for coding variants: http://denovo-db.gs.washington.edu/denovo-db/QueryVariantServlet?searchBy=Gene&target=MAPK8IP3 ------------ NM_015133.4:c.111C>G (p.Tyr37Ter) has been submitted in ClinVar by the Undiagnosed Diseases Network (NIH) as likely pathogenic, associated with MAPK8IP3-related disorder (hypotonia, DD, EEG anomalies among the phenotypes). It is not clear whether this subject corresponds to individual #3 reported by the previous study (possibly not the case). ------------ MAPK8IP3 is not associated with any phenotype in OMIM, nor in G2P. This gene is not commonly included in gene panels for ID. ------------ As a result, MAPK8IP3 can be considered for inclusion in this panel as green (rather than amber). Sources: Literature |
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| Intellectual disability - microarray and sequencing v2.588 | CWF19L1 |
Konstantinos Varvagiannis gene: CWF19L1 was added gene: CWF19L1 was added to Intellectual disability. Sources: Literature,Radboud University Medical Center, Nijmegen Mode of inheritance for gene: CWF19L1 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: CWF19L1 were set to 25361784 Phenotypes for gene: CWF19L1 were set to Spinocerebellar ataxia, autosomal recessive 17 (MIM 616127) Penetrance for gene: CWF19L1 were set to Complete Review for gene: CWF19L1 was set to GREEN gene: CWF19L1 was marked as current diagnostic Added comment: Biallelic pathogenic variants in CWF19L1 cause Spinocerebellar ataxia, autosomal recessive 17 (MIM 616127). ------- Burns et al. (2014 - PMID: 25361784) report on 2 sibs born to consanguineous parents, homozygous for a splice site variant (NM_018294.5:c.964+1G>A). Congenital ataxia with hypoplasia of vermis and cerebellar hemispheres and ID were features reported in both in this study. Clinical details on this family were published previously (Yapici and Eraksoy - PMID: 15981765) where ID appeared to be a feature for one of the sibs (FSIQ of 68) but not the other (IQ of 90) [the sibs seem to correspond to patients 5 and 6 from the third family of the original report]. Expression in patient lymphoblastoid cell lines was reduced using expression micro-arrays and quantitative reverse-transcription PCR. The variant was shown to lead to skipping of exon 9. Introduction of an out-of-frame stop codon (thus NMD) may explain mRNA levels. Western blot using epitope spanning exons 5-7 demonstrated absence (in patient but not in control LCLs) of the 2 protein bands expected based on this epitope. [A shorter isoform due to downstream alternative start site would not be detectable]. Using commercial normal tissue brain lysates revealed only the canonical protein band suggesting that this is the isoform present in brain. Morpholino knockdown of cwf91l1 in zebrafish resulted in altered cerebellar staining (/structure) and abnormal motor behavior. -------- Nguyen et al. (2016 - PMID: 26197978) report on a further individual with ID, ataxia and abnormal cerebellum (extensive discussions whether this represents hypoplasia/atrophy) compound heterozygous for a missense (NM_018294.4:c.37G>C / p.Asp13His) and a nonsense variant (c.946A>T / p.Lys316*). mRNA expression in patient fibroblasts was similar to control while cDNA sequence analysis was suggestive of lower levels for the r.946A>U transcript (compared to r.37G>C) possibly due to NMD. -------- Evers et al. (2016 - PMID: 27016154) report on a further individual, born to consanguineous parents, homozygous a frameshift variant (NM_018294.5:c.467delC or p.Pro156Hisfs). This individual presented with ID, ataxia and similar cerebellar anomalies. cDNA of 3 different regions of CWF19L1 suggested tht mRNA was not entirely degraded by NMD. Western blot demonstrated absence of a band corresponding to the longest isoform in patient LCL cells. [All isoforms discussed in Fig3]. A subsequent pregnancy of the same couple was terminated due to presence of additional fetal anomalies possibly not explained by homozygosity (only) for this variant which was confirmed (cerebellar measurements were in the the low-normal range and morphology reportedly normal). -------- In ClinVar additional variants have been submitted as pathogenic/likely pathogenic (although a phenotype is not specified for all). -------- CWF19L1 is not associated with any phenotype in G2P. This gene is included in gene panels for ID offered by diagnostic laboratories (incl. Radboudumc). -------- As a result CWF19L1 can be considered for inclusion in this panel probably as green (rather than amber). Sources: Literature, Radboud University Medical Center, Nijmegen |
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| Intellectual disability - microarray and sequencing v2.588 | PTRH2 |
Konstantinos Varvagiannis gene: PTRH2 was added gene: PTRH2 was added to Intellectual disability. Sources: Literature,Radboud University Medical Center, Nijmegen Mode of inheritance for gene: PTRH2 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: PTRH2 were set to 25574476; 27129381; 25558065; 28328138; 28175314 Phenotypes for gene: PTRH2 were set to Infantile-onset multisystem neurologic, endocrine, and pancreatic disease (MIM 616263) Penetrance for gene: PTRH2 were set to Complete Review for gene: PTRH2 was set to GREEN gene: PTRH2 was marked as current diagnostic Added comment: Biallelic pathogenic variants in PTRH2 cause Infantile-onset multisystem neurologic, endocrine, and pancreatic disease (MIM 616263). Several affected individuals have been reported to date. ID was a feature in the majority. Hu et al. (2014 - PMID:25574476) reported on 2 sibs born to consanguineous Yazidian-Turkish family, homozygous for a frameshift variant [NM_016077.4(PTRH2):c.269_270delCT (p.Ala90Glyfs)]. In PMID: 27129381 (2016) the same group reported on 5 additional individuals, from 2 unrelated consanguineous (Tunesian / Saudi-Arabian) pedigrees. These subjects were homozygous for a missense variant [NM_016077.4(PTRH2):c.254A>C (p.Gln85Pro)]. A summary of the features observed in all 7 cases is provided in table 1 of the latter article. ID was a feature in all 6 individuals for whom this information was available (6/7). Phenotypic variability even among individuals with the same variant is underscored. mRNA studies for both variants have shown similar levels compared to controls, with reduced protein upon Western blot (for both). In Ptrh2-null mouse model a similar to the human phenotype is observed (muscle weakness and wasting, ataxia, cerebelar atrophy, etc.) (PMIDs:25574476 and 28175314). Alazami et al. (PMID: 25558065 - 2015) report on an additional individual homozygous for the p.Gln85Pro variant. This boy presented with intellectual disability (clinical details provided in the supplement). Sharkia et al. (PMID: 28328138) describe 3 sibs homozygous for the p.Gln85Pro variant. The index patient was reported to have normal intelligence upon formal testing which also appeared to be the case for her 2 sisters. Apart from the 2 variants observed in the published patients, 2 further variants have been submitted in ClinVar as likely pathogenic, namely : NM_016077.4(PTRH2):c.253C>T (p.Gln85Ter) and NM_001015509.2(PTRH2):c.114dup (p.Gly39Trpfs). PTRH2 is not associated with any phenotype in G2P. This gene is included in gene panels for intellectual disability offered by diagnostic laboratories (incl. Radboudumc). As a result it can be considered for inclusion in the ID panel as green (or amber). [As several individuals presented with ataxia, demyelinating sensorimotor neuropathy, sensorineural hearing loss and other possibly relevant phenotypes, consider inclusion in the respective gene panels]. Sources: Literature, Radboud University Medical Center, Nijmegen |
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| Intellectual disability - microarray and sequencing v2.584 | ZBTB11 |
Konstantinos Varvagiannis gene: ZBTB11 was added gene: ZBTB11 was added to Intellectual disability. Sources: Literature Mode of inheritance for gene: ZBTB11 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: ZBTB11 were set to 29893856; 28382966 Phenotypes for gene: ZBTB11 were set to Intellectual disability Penetrance for gene: ZBTB11 were set to Complete Review for gene: ZBTB11 was set to AMBER Added comment: Fattahi et al. (PMID: 29893856) report on 9 individuals from 2 broader consanguineous pedigrees with biallelic ZBTB11 mutations. Features in the first family (from Iran) consisted of moderate ID, microcephaly, ataxic gait, and spasticity with MRI findings of cerebellar atrophy and ventriculomegaly. Individuals from the second family (from Pakistan) presented with moderate ID and variable features. Homozygosity for missense ZBTB11 variants, private to each family was shown (NM_014415.3:c.2185C>T / p.H729Y and c.2640T>G / p.H880Q for the first and second family respectively). As the authors note, ZBTB11 is predicted to be a zinc finger transcriptional regulator and one of the hypotheses emitted suggests possible disruption of DNA binding. Functional studies performed demonstrated that the mutant proteins were excluded from the nucleolus where the (wt) protein localizes. Previous zebrafish models (PMID: 28382966) suggested CNS degeneration among other phenotypes in Zbtb11 mutants. Knockdown of the drosophila ZBTB11-ortholog (CkIIα-i1) resulted in recognizable shrinking of the mushroom body with significant reduction in the number of neurons compared to controls. Other Zinc Finger and BTB Domain-Containing proteins cause disorders with ID as a prominent feature (eg. ZBTB16, ZBTB20, etc.). ZBTB11 is not associated with any phenotype in OMIM nor in G2P. As a result, this gene can be considered for inclusion in this panel probably as amber (2 pedigrees only) or green (given the supportive functional studies). Sources: Literature |
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| Intellectual disability - microarray and sequencing v2.584 | AIMP2 |
Konstantinos Varvagiannis gene: AIMP2 was added gene: AIMP2 was added to Intellectual disability. Sources: Literature,Radboud University Medical Center, Nijmegen Mode of inheritance for gene: AIMP2 was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: AIMP2 were set to 29215095 Phenotypes for gene: AIMP2 were set to Leukodystrophy, hypomyelinating, 17 (MIM 618006) Penetrance for gene: AIMP2 were set to Complete Review for gene: AIMP2 was set to AMBER gene: AIMP2 was marked as current diagnostic Added comment: Biallelic pathogenic variants in AIMP2 cause Leukodystrophy, hypomyelinating, 17 (MIM 618006). 3 individuals from 2 unrelated consanguineous families, of Indian origin have been reported (all in PMID: 29215095). The phenotype consisted of feeding difficulties, lack of development with intellectual disability and seizures as well as brain MRI abnormalities (cerebral and cerebellar atrophy, hypo-intensities of the basal ganglia on T2w sequences). Severe microcephaly was observed in 2 patients for whom this information was available (birth measurements not specified). All patients described to date were homozygous for a nonsense variant [NM_006303.3:c.105C>A or p.(Tyr35Ter)] which appears to be a founder mutation in this population. Quantitative reverse transcription PCR demonstrated reduced mRNA levels in peripheral lymphocytes, but this decrease was not significant compared to controls (the authors presume low level of NMD). Previous mouse models provide some - but not substantial - support. The authors note marked similarity with the phenotype associated with AIMP1 (Leukodystrophy, hypomyelinating, 3 - MIM 260600), another auxiliary protein of the macromolecular multienzyme multi-tRNA synthetase complex. AIMP1 is listed in the current panel as green. AIMP2 is not associated with any phenotype in G2P. This gene is included in gene panels for ID offered by some diagnostic laboratories (incl. Radboudumc). As a result, AIMP2 can be considered for inclusion in this panel probably as amber. Sources: Literature, Radboud University Medical Center, Nijmegen |
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| Intellectual disability - microarray and sequencing v2.550 | UFM1 |
Konstantinos Varvagiannis gene: UFM1 was added gene: UFM1 was added to Intellectual disability. Sources: Literature,Expert Review Mode of inheritance for gene: UFM1 was set to BOTH monoallelic and biallelic, autosomal or pseudoautosomal Publications for gene: UFM1 were set to 28931644; 29868776 Phenotypes for gene: UFM1 were set to Leukodystrophy hypomyelinating 14, 617899 Penetrance for gene: UFM1 were set to Complete Review for gene: UFM1 was set to GREEN Added comment: Biallelic UFM1 mutations cause Leukodystrophy hypomyelinating 14, MIM 617899. PMID: 28931644 is the first report on 16 individuals from 14 families with shared Roma ethnic background. All subjects were found to harbor a UFM1 promoter 3 basepair deletion in the homozygous state. All patients demonstrated a severe phenotype including lack of development and severe epileptic encephalopathy while their MRI images demonstrated hypomyelination with atrophy of the basal ganglia and the cerebellum. The promoter deletion was detected by exome sequencing. Previously a 0.8 Mb homozygous region was identified to be shared by all the patients in whom a SNP array was performed. Alternative causes, notably TUBB4A mutations and deletions/duplications were excluded. 3 individuals had Sanger sequencing of all coding regions within the homozygous interval to rule out other - eventually missed - variants. PMID: 29868776 reports 4 additional individuals from 2 consanguineous families (one from Ethiopia, for the other this was not specified). All 4 patients were homozygous for the c.241C>T (NM_016617.3) or p.(Arg81Cys) variant which was shown to be hypomorphic upon functional studies. The phenotype consisted of developmental delay (4/4 or 20/20 including the patients from the previous report with which comparison is made in table 2 of the article) with microcephaly (4/4 or 20/20) and seizures (4/4 or 16/20) as well as MRI abnormalities. Failure to thrive and/or short stature were also among the most common features. UFM1 (as well as UFC1 also discussed in the same article) participate in ufmylation, with mutations in other enzymes of the same process (notably UBA5 - gene rated Green in the ID and epilepsy panels) having already been described in neurodevelopmental disorders. As a result, this gene can be considered for inclusion in this panel as green (or amber). Sources: Literature, Expert Review |
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| Intellectual disability - microarray and sequencing v2.528 | ADPRHL2 | Louise Daugherty Added comment: Comment on list classification: New gene added by external reviewer as Amber. However, majority of people have seizures and only a minority have some intellectual component and this seems to later onset /developmental regression, the clinical picture is one of a stress-induced neurodegenerative disease of variable progression with developmental delay, intellectual disability, mild cerebellar atrophy and recurring seizures. However I am not sure if this gene is within the scope of the ID panel and as they all present with seizures so is better presented on Genetic Epilepsy Syndromes panel. So pending further cases/evidence will leave gene as Amber and watchlist | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v2.510 | EMC1 |
Konstantinos Varvagiannis gene: EMC1 was added gene: EMC1 was added to Intellectual disability. Sources: Expert Review,Literature Mode of inheritance for gene: EMC1 was set to BOTH monoallelic and biallelic (but BIALLELIC mutations cause a more SEVERE disease form), autosomal or pseudoautosomal Publications for gene: EMC1 were set to 26942288; 29271071 Phenotypes for gene: EMC1 were set to Cerebellar atrophy, visual impairment, and psychomotor retardation, MIM 616875 Penetrance for gene: EMC1 were set to Complete Review for gene: EMC1 was set to GREEN gene: EMC1 was marked as current diagnostic Added comment: Harel et al. (PMID: 26942288) describe 7 individuals from 3 families with biallelic pathogenic variants in EMC1. In the first family, a single individual (born to non-consanguineous parents) was found to harbor a homozygous frameshift variant in a small (approx. 100 kb) stretch of absence of heterozygosity. The patients in the other two families were homozygous for missense variants (private to each family) in the context of parental consanguinity. The common phenotype was suggestive of a progressive neurodegenerative disorder and consisted of hypotonia, severe developmental delay with marked speech delay, diminished deep tendon reflexes, cerebellar atrophy, vision as well as skeletal problems. Seizures were a feature in one subject. One further patient from an additional (fourth) family was found to have a similar but milder phenotype and was only found to harbor a de novo missense variant in EMC1 following trio exome sequencing. Sanger sequencing of the promoter region as well as CNV calling from the exome data failed to reveal other variants in this specific individual. Similarly to what has been observed in other genes the authors propose that both monoallelic and biallelic pathogenic variants may be causative of the specific phenotype, though the presentation may be more severe in case of biallelic variants. Altogether this study reports 1 homozygous frameshift and 3 missense variants (2 of the latter found in homozygous state and one as a de novo heterozygous mutation). // Geetha et al. (PMID: 29271071) describe an individual born to consanguineous parents presenting with hypotonia, developmental delay, and cerebellar atrophy as well as early onset epilepsy. Exome sequencing demonstrated a homozygous splice variant in EMC1. This variant was demonstrated to result to retention of intron 11 upon RNA sequencing. This was predicted to lead to premature truncation of the protein. // EMC1 is associated in OMIM with Cerebellar atrophy, visual impairment, and psychomotor retardation (MIM 616875) for which an autosomal recessive inheritance mode is retained. // Apart from the variants reported in the previous studies [p.Pro874Argfs*21, p.Thr82Met, p.Gly868Arg, p.Gly471Arg, c.1212+1G>A - NM_015047.2] further variants have been submitted in ClinVar as likely pathogenic (Variation IDs : 521479, 445564). // The gene has been included in intellectual disability gene panels offered by a few other diagnostic labs. // As a result this gene can be considered for inclusion in the panel as green (or amber). Sources: Expert Review, Literature |
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| Intellectual disability - microarray and sequencing v2.510 | VARS |
Konstantinos Varvagiannis gene: VARS was added gene: VARS was added to Intellectual disability. Sources: Expert Review,Literature Mode of inheritance for gene: VARS was set to BIALLELIC, autosomal or pseudoautosomal Publications for gene: VARS were set to 26539891; 29691655; 30275004 Phenotypes for gene: VARS were set to # 617802. NEURODEVELOPMENTAL DISORDER WITH MICROCEPHALY, SEIZURES, AND CORTICAL ATROPHY; NDMSCA Penetrance for gene: VARS were set to Complete Review for gene: VARS was set to GREEN gene: VARS was marked as current diagnostic Added comment: PMID: 26539891 is the first report on individuals with biallelic pathogenic variants in VARS. 3 individuals from 2 consanguineous families are briefly reported. The phenotype was similar in all 3, consisting of severe developmental delay, microcephaly, seizures and cortical atrophy. Subjects from the first family were homozygous for a missense variant in the tRNA synthetase catalytic domain [p.(L885F)]. The patient from the second family was homozygous for a missense SNV affecting the anticodon-binding domain [p.(R1058Q)]. PMID: 29691655 reports on a further patient born to non-consanguineous parents, with 2 in-trans pathogenic variants in VARS. The phenotype consisted of progressive microcephaly (OFC at birth -2SD, at the age of 2 months -4SD), global developmental delay, seizures and progressive cerebral and cerebellar atrophy. An affected brother presented with more severe phenotype (OFC -6SD at birth and -8SD at 2 months of age), seizures, hearing loss but was deceased and unavailable for genetic testing. cDNA studies demonstrated absence of the reference allele for the missense mutation downstream the splice variant (in line with a reduced or absent mRNA allele harboring the splice variant). Similarly, mRNA expression studies demonstrated 50-60% reduction in the transcripts (due to NMD of the allele with the splice SNV). Western blot showed severe reduction in protein levels (more pronounced compared to what would be expected by mRNA expression) presumably secondary to decreased protein stability due to the missense variant. Severe defects in aminoacylation were further confirmatory of a pathogenic role of these variants. The missense variant was affecting the anticodon-binding domain, important for aminoacylation. PMID: 30275004 reports on 2 siblings with developmental delay, intellectual disability, severe speech impairment and microcephaly, similar to what has been described for the disorder. Clinical findings were somewhat different from previous studies in that microcephaly was acquired, while seizures and cortical atrophy were not part of the phenotype. Both sibs were compound heterozygous for 2 missense variants, though only one of these mutations affected the anticodon binding domain and the other was in the N-terminal region of the protein. Previous metabolic studies and extensive genetic testing (karyotype, CMA, MECP2, FMR1) was normal. Epilepsy was a feature in 4 of the 6 individuals for whom genetic testing was possible (or 5/7 in total). VARS belongs to the family of amino acyl-tRNA synthetases (ARSs). Mutations in several cytoplasmic ARSs are associated with severe neurological manifestations including seizures, intellectual disability associated with microcephaly. VARS is included in gene panels for intellectual disability (but not for epilepsy) offered by different diagnostic labs. As a result this gene can be considered for inclusion in the ID and epilepsy panel as green (or amber). Sources: Expert Review, Literature |
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| Intellectual disability - microarray and sequencing v2.468 | ATRX | Louise Daugherty Source Victorian Clinical Genetics Services was added to ATRX. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing v2.398 | ISCA-37418-Gain |
Louise Daugherty Region: ISCA-37418-Gain was added Region: ISCA-37418-Gain was added to Intellectual disability. Sources: ClinGen,Expert Review Green Mode of inheritance for Region: ISCA-37418-Gain was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Phenotypes for Region: ISCA-37418-Gain were set to infantile hypotonia, failure to thrive, mental retardation, autistic features, sleep apnea, and structural cardiovascular anomalies; 610883; characterized by hypotonia, poor feeding, failure to thrive, developmental delay, mild-moderate intellectual deficit, and neuropsychiatric disorders. Structural cardiovascular anomalies (dilated aortic root, bicommissural aortic valve, atrial/ventricular and septal defects) and sleep disturbance (obstructive and central sleep apnea) are also frequently associated |
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| Intellectual disability - microarray and sequencing v2.398 | ISCA-37418-Loss |
Louise Daugherty Region: ISCA-37418-Loss was added Region: ISCA-37418-Loss was added to Intellectual disability. Sources: ClinGen,Expert Review Green Mode of inheritance for Region: ISCA-37418-Loss was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Phenotypes for Region: ISCA-37418-Loss were set to Potocki-Lupski syndrome; hypotonia, poor feeding, failure to thrive, developmental delay particularly cognitive and language deficity, mild-moderate intellectual deficit, and neuropsychiatric disorders; Smith-Magenis syndrome; Structural cardiovascular anomalies (dilated aortic root, bicommissural aortic valve, atrial/ventricular and septal defects) and sleep disturbance; 182290; moderate intellectual disability, delayed speech and language skills, distinctive facial features, sleep disturbances, and behavioral problems; hypotonia, failure to thrive, mental retardation, pervasive developmental disorders, congenital anomalies; Dental abnormalities |
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| Intellectual disability - microarray and sequencing v2.398 | ISCA-37421-Gain |
Louise Daugherty Region: ISCA-37421-Gain was added Region: ISCA-37421-Gain was added to Intellectual disability. Sources: ClinGen,Expert Review Green Mode of inheritance for Region: ISCA-37421-Gain was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for Region: ISCA-37421-Gain were set to 3298277; 3817079 Phenotypes for Region: ISCA-37421-Gain were set to Chromosome 1q21.1 duplication syndrome; ncomplete penetrance and variable expression characterized by macrocephaly, developmental delay, intellectual disability, psychiatric disturbances (autism spectrum disorder, attention deficit hyperactivity disorder, schizophrenia, mood disorders) and mild facial dysmorphism (high forehead, hypertelorism). Other associated features include congenital heart defects, hypotonia, short stature, scoliosis; 612475; 1q21.1 microduplication syndrome |
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| Intellectual disability - microarray and sequencing v2.398 | ISCA-37423-Gain |
Louise Daugherty Region: ISCA-37423-Gain was added Region: ISCA-37423-Gain was added to Intellectual disability. Sources: ClinGen,Expert Review Green Mode of inheritance for Region: ISCA-37423-Gain was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for Region: ISCA-37423-Gain were set to 21933911; 23345203 Phenotypes for Region: ISCA-37423-Gain were set to Behavioral problems, cleft lip and/or palate, macrocephaly, and seizures were confirmed as additional features among the new patients, and novel features included neonatal respiratory distress, attention deficit hyperactivity disorder (ADHD), ocular anomalies, balance problems, hypotonia, and hydrocele.; mild to moderate developmental delay, intellectual disability, mild facial dysmorphism (incl. prominent forehead, arched eyebrows, broad nasal bridge, upturned nares, cleft lip and/or palate) and congenital cardiac anomalies (e.g., atrioventricular septal defect). Other reported features include macrocephaly, behavioral abnormalities (e.g., attention deficit disorder), seizures, hypotonia and ocular and digital anomalies (poly/syndactyly); congenital heart disease; 8p23.1 duplication syndrome |
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| Intellectual disability - microarray and sequencing v2.398 | ISCA-37423-Loss |
Louise Daugherty Region: ISCA-37423-Loss was added Region: ISCA-37423-Loss was added to Intellectual disability. Sources: ClinGen,Expert Review Green Mode of inheritance for Region: ISCA-37423-Loss was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for Region: ISCA-37423-Loss were set to 23239632; 20969981 Phenotypes for Region: ISCA-37423-Loss were set to prenatal and postnatal growth retardation, low birth weight, mild to moderate intellectual deficit, psychomotor retardation, poor speech, seizures, behavioral problems such as hyperactivity and impulsiveness. Frequent craniofacial abnormalities include microcephaly, high and narrow forehead, broad nasal bridge, epicanthic folds, high arched palate, short neck and low set unusually shaped ears. Furthermore congenital heart defects (atrioventricular, septal defects, pulmonary stenosis), congenital diaphragmatic hernia and in boys cryptorchidism and hypospadias have been frequently reported.; congenital heart defects, microcephaly, psychomotor delay and behavioural problems; hyperactivity, craniofacial abnormalities; 8p23.1 microdeletion syndrome; moderate intellectual disability |
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| Intellectual disability - microarray and sequencing v2.398 | ISCA-37430-Loss |
Louise Daugherty Region: ISCA-37430-Loss was added Region: ISCA-37430-Loss was added to Intellectual disability. Sources: ClinGen,Expert Review Green Mode of inheritance for Region: ISCA-37430-Loss was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Phenotypes for Region: ISCA-37430-Loss were set to microcephaly, dysgenesis of the corpus callosum, and cerebellar atrophy, as well as neurobehavioral disorders, including delayed development, mental retardation, and attention deficit-hyperactivity disorder. Patients with duplications of YWHAE tended to have macrosomia, facial dysmorphism, and mild developmental delay; growth restriction, craniofacial dysmorphisms, structural abnormalities of brain and cognitive impairment; Chromosome 17p13.3 duplication syndrome; prominent forehead, bitemporal hollowing, short nose with upturned nares, protuberant upper lip, thin vermilion border, and small jaw; Characteristic facies, pre- and post-natal growth retardation; 247200; classic lissencephaly (pachygyria, incomplete or absent gyration of the cerebrum), microcephaly, wrinkled skin over the glabella and frontal suture, prominent occiput, narrow forehead, downward slanting palpebral fissures, small nose and chin, cardiac malformations, hypoplastic male extrenal genitalia, growth retardation, and mental deficiency with seizures and EEG abnormalities; Miller-Dieker lissencephaly syndrome |
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| Intellectual disability - microarray and sequencing v2.398 | ISCA-37432-Loss |
Louise Daugherty Region: ISCA-37432-Loss was added Region: ISCA-37432-Loss was added to Intellectual disability. Sources: ClinGen,Expert Review Green Mode of inheritance for Region: ISCA-37432-Loss was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Phenotypes for Region: ISCA-37432-Loss were set to RCAD syndrome; utero-vaginal atresia; Schizophrenia; 614527; delayed development, intellectual disability; Renal cysts and diabetes syndrome; Autism Spectrum Disorder; Mayer-Rokitansky-Kster-Hauser (MRKH) syndrome in females; Chromosome 17q12 deletion syndrome; global developmental delay |
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| Intellectual disability - microarray and sequencing v2.398 | ISCA-37443-Loss |
Louise Daugherty Region: ISCA-37443-Loss was added Region: ISCA-37443-Loss was added to Intellectual disability. Sources: ClinGen,Expert Review Green Mode of inheritance for Region: ISCA-37443-Loss was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Phenotypes for Region: ISCA-37443-Loss were set to . mild to moderate mental retardation, with only slightly dysmorphic facial features that were similar in most patients: long and narrow face, short philtrum, and high nasal bridge. Autism, gait ataxia, chest wall deformity, and long and tapering fingers were noted in at least 2 of the 6 patients. delayed psychomotor development with mild to moderate mental retardation and/or learning disabilities with speech delay. All had low birth weight, microcephaly, high nasal bridge, and short philtrum, and 3 had clinodactyly of the toes. primary pulmonary hypertension, patent ductus arteriosus (PDA), subvalvular aortic stenosis, and gastroesophageal reflux, and required neonatal intensive care for 57 days after birth due to complications of meconium aspiration. He had mild dysmorphic features, including posteriorly rotated ears, shallow orbits, frontal bossing, prominent nose, long thin lip, and broad face. He also had bilateral sandal gap toes, single palmar creases, and bilateral inguinal hernia. However, he was developmentally normal at age 6 months. delayed psychomotor development with delayed waking and poor motor skills, autism with speech delay, mental retardation, and psychiatric disturbances, including aggression, anxiety, hyperactivity, and bipolar disorder with psychosis in 1. Both had dysmorphic features, including high nasal bridge, asymmetric face, and crowded/dysplastic teeth; 1 had micrognathia and epicanthal folds. Both had tapered fingers. 609425; Chromosome 3q29 microdeletion syndrome |
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| Intellectual disability - microarray and sequencing v2.398 | ISCA-37408-Loss |
Louise Daugherty Region: ISCA-37408-Loss was added Region: ISCA-37408-Loss was added to Intellectual disability. Sources: ClinGen,Expert Review Green Mode of inheritance for Region: ISCA-37408-Loss was set to MONOALLELIC, autosomal or pseudoautosomal, imprinted status unknown Publications for Region: ISCA-37408-Loss were set to 16963482; 22579565; 18245392 Phenotypes for Region: ISCA-37408-Loss were set to PMID: 16963482 idiopathic intellectual disability including moderate to severe intellectual disability, autism/autistic features, microcephaly, structural brain anomalies including cortical dysplasia/pachygyria, renal anomalies (multicystic kidney, hydronephrosis), digital camptodactyly, visual impairment, strabismus, neuromotor deficits, communication and attention impairments, and a distinctive pattern of craniofacial features. Dysmorphic craniofacial features include progressive microcephaly, flat occiput, widened inner canthal distance, small palpebral fissures, ptosis, long and straight eyelashes, broad and high nasal root extending to a widened, prominent nasal tip with elongated, smooth philtrum, rounding of the upper vermillion border and everted lower lips. PMID: 18245392 A 32-year-old, mentally retarded male was referred to our centre for further clinical genetic analysis. He was born to non-consanguineous parents after 42 weeks gestation with a birth weight of 3500 g. He had a healthy older brother. In the neonatal period he was hypotonic and at 8 weeks of age he underwent surgery because of an inguinal hernia with removal of an atrophic right testis. His motor development was severely delayed with sitting at 3.5 years and walking at 5 years of age. Speech was poorly developed, characterised by the usage of only a few words. During infancy an optic nerve hypoplasia was diagnosed, and during childhood he frequently suffered from luxations of the patellae, which required surgery. At the age of 32 years his height is 163 cm (_3 SDS) and head circumference 52.5 cm (_2.5 SDS). He has a narrow receding forehead, widened inner canthal distance of 3.5 cm (90th centile), normal outer canthal distance of 8.5 cm (25th centile), telecanthus, short and down slanting palpebral fissures, epicanthal folds, ptosis, long, straight eyelashes, high nasal bridge, low set large ears, flat philtrum, small mouth with high, narrow palate and retrognathia. The thorax is broad with increased internipple distance and slight gynaecomastia. A recent renal ultrasound revealed multiple cysts in the left, dystrophic kidney and two uncomplicated cysts in the enlarged, right kidney. The patient has a normally sized phallus with absent right testis and small left testis. His hands show a simian crease right and tapering fingers with broad proximal interphalangeal joints. He shows sandal gaps on both flat feet with clinodactyly of the fourth and fifth toes (and more); 612513; PMID: 22579565 severe developmental delay, congenital microcephaly, intractable epilepsy, and renal anomalies, as well as a congenital choledochal cyst which has not been previously reported in other patients with this cytogenetic defect |
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| Intellectual disability - microarray and sequencing | ATRX | BRIDGE consortium edited their review of ATRX | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing | ATRX | BRIDGE consortium edited their review of ATRX | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Intellectual disability - microarray and sequencing | ATRX | BRIDGE consortium reviewed ATRX | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||